It is not difficult to keep aquarium fish healthy and colourful.  There are several basic requirements to follow to ensure the best care for your pet fish.  You only need to spend a few minutes a day to keep your fish happy and give yourself the satisfaction of having a tank full of healthy fishes and beautiful plants.

The basic requirements are:

Proper housing
Proper pumps and filtering systems
Water condition and stress control
Correct nutritional requirements in feeding
Careful observation daily while Checking for signs of diseases
Understanding of diseases
Diagnosis and Treatment of diseases
Correct usage of aquarium pharmaceuticals

Frequently Asked Questions (FAQ)
Tips on Fish Keeping

World Yellow PagesWorld Yellow Pages


Human beings build or buy their homes depending on their financial capabilities and requirements. If they are not happy with their neighbours they can move to another location of their choice.   Unfortunately the aquarium fishes live in whatever space we provide them and we choose the company they keep.  Therefore, before you buy any aquarium you must first decide the types of fish you like to have.  In this way you can design a housing system close to their natural habitat.  It is also easier to keep the same species of fish together in one aquarium.  You can also keep fishes of different  species provided they are compatible with one another, have same nutritional requirements, and can live in similar water conditions in the same community tank.  Try not to keep hard water and soft water species together or solely carnivorous (meat eater) and vegetarian species together.  However most aquarium fishes are omnivorous, eating a combined diet and these species can live with carnivorous and vegetarian species.  Some fish (such as Oscar fish) can grow up to 8 inches or more in size and it is unwise to keep them with Tetra species that hardly grow up to 2 inches.

Whether you like big or small fishes, be prepared to change to a bigger tank when the fishes you first keep have grown in size.  Generally, an average of 15 square unit of surface area may accommodate one unit of body length of aquarium fish (tail excluded). You can calculate the sizes of the tank required for the maximum quantity of fish you decided to keep.  For example, if you start with 5 goldfish 1” in size in a 10 gallon tank, be prepared to buy a 40 gallon tank when they grow to 3” in size and so on.  It is very cruel to keep the grown up fish in the same 10-gallon tank although they may survive with proper aeration and filtering system.  They must have enough space to swim freely to be healthy and free from diseases.

Keep a good aquarium book as reference on the types of fish suitable for a community tank.

Back to Page 1


There are many types of pumps and filters available for sale in the aquarium trade. You must choose one that is most suitable for your purpose and not the most expensive . If you are keeping Koi or goldfish, you will need a more elaborate system than if you are only keeping a few guppies.  Whatever system you select, you must bear in mind that your duty is to give the captive fishes a system that is closest to their natural habitat.


Air pumps, such as power pumps, overhead pumps, vibrator pumps and piston pumps, are used to pump air (atmospheric air) into the aquarium.  Those pumps that pump water into the aquariums or ponds are not normally used in home aquarium.  For home aquarium use, the most popular types are the power and vibrator pumps.  Use the power pump with high capacity filter for bigger aquarium and for fish that  by nature produces considerable quantities of waste  --  gold fish and Koi are typical example, especially when they are overfed.
Use the double vibrator pumps with the most numbers of controllable outlets you can  find for your aquarium.  The more outlets you have the more flexibility you can get for driving more aerating stones and the different types of ornamentals.

A small inside filter such as a corner or box bubble filter  will serve the purpose for a small aquarium of about 10-gallon.  To improve filtering efficiency you may use more than one box filter or a bigger-sized box filter in the same aquarium.  For the bigger aquarium -- about 30 gallons and above, use under gravel filters (also known as biological filters) if your main interest is keeping all sorts of small sizes tropical fishes.  Use suitable gravel for your under gravel filters and choose the right type of plants. Use pebbles with coarse sand for most acid and soft water fishes.   Do not use marble chips or coral sand unless you are keeping hard water and alkaline loving fishes or marine fish.  If you preferred bigger fishes (more than 3 inches) such as gold fish, Koi, Oscar, or cichlids - it is more economical to use several box filters in one tank without gravel or plants. Most bigger fish uproot plants for fun while some enjoy eating and nibbling them. If you like to plant your aquarium please check the habits of your fish with the experienced hobbyists or refer to aquarium books before you start.

Another types of overhead filters come with small size suction pumps which pump water to the top of the tank and allow water to filter through by gravity force are efficient combination for use in small aquarium with less than 10 gallon of water.

When you have a bigger aquarium of 20 gallons or more, overhead filters are not the best choice.  The filtering media become choked up easily and overflow all over the floor while the pump burnt out whenever you forget to check the water level of the aquarium.  The outside filters, whether power or air operated, are also very popular but you have to check the filtering media regularly; otherwise you will have to mop the floor daily.
There is another popular filtering equipment, which is actually an electric pump combined with  built-in filters.  These pumps are specially made for use inside or outside the aquarium.  With proper attachments, cleaning of pumps and filters are neat and non-messy. Some good quality external or internal power filters such as the Eheim or Vortex series are very efficient but costly.

Be careful if you intend to use Nitrifying bacteria for your biological systems.  These live nitrifying bacteria, some marketed as 'enzyme' are already dead even before they reach your tank, especially the liquid form.  Commercial preparations of nitrifying bacteria often fail because they are sold well beyond the expected shelf life.

However, if you insist on using the nitrifying bacteria, buy the powder form  with expiry date indication from reputable aquarium shops.  Please remember that even the best quality liquid type have less than one year shelf life (most have only six month shelf life).  The biggest users of these products are the aquaculture companies (breeders of food fish, prawns, eel, etc.); water and sewage treatment companies but not the aquarium trade.

Your properly set up tank with stabilised, matured and correct filtering media may contain more bacteria than the bottle you pay at fantastic price.

Back to Page 1


Water to fish is like air to humans.  Fish will not survived if water is polluted with harmful toxins or the chemistry of water is not suitable for their survival.  Different species of fishes require different range of water conditions for their well-being.  However, most fishes are able to live happily within a common range of water conditions.
As hobbyists, we group them together and provide them with the best conditions for their survival within an aquarium.

Fishes selected for a community tank must be able to tolerate the same range of water conditions such as water hardness, temperature and pH level; otherwise some fishes in the same aquarium may look sick while others seem to be very healthy.  Poor water conditions lead to stress in captive fish.  Stress weakens their immune systems, leading to increased susceptibility to disease.  Some of the most common stress problems and their causes in aquarium fish are:

Back to Page 1


A fish must eat the right quantity and quality of food to stay healthy. The aquarium fish depends entirely on their keeper to provide them with an appropriate, well-balanced diet. The keeper must at least know that their fish needs protein to replace the body cells as they wear out, carbohydrate to provide energy and warmth, vitamins and minerals to help various organs to function properly and to fight against diseases.
To supply the fish with a varied but balanced diet, the keeper must be able to source for high quality flake or pellet food and supplement with good quality fresh live food. Make sure you buy only the quality flake or pellet food with full display of analyzed ingredients manufactured by reputable manufacturers.  In Singapore and Malaysia, there are many pellet foods packed in Japanese language plastic bags or containers containing nothing but high starch with low protein contents.  There are live food (daphnia, bloodworms and tubifex worms) available in the aquarium shops, but these are also the main source of bacteria and parasites entering the aquarium.
The best live food is the freshly hatched brine shrimps but they are very small and more suitable for small fish.
The next alternatives are the freeze-dried food.  The freeze-dried Krill, bloodworms, daphnia and tubifex worms are good quality food in addition to the flake or pellet food.  Do not use frozen food unless you know the source of supply because they could be unsold live worms frozen overnight.

A number of vitamins and minerals liquid supplements have recently appeared in the aquarium market.  In their form their therapeutic values are very doubtful.  Firstly, not all vitamins and minerals are water-soluble.  If they are insoluble in water, the fish is unable to absorb the contents through its gills -- the way it absorbs oxygen; by simple diffusion.

Water-soluble vitamins such as ascorbic acid, pyridoxine, thiamine, choline, folic acid, riboflavine, pantothenic acid, B12, nicotinic acid, biotin and water-diffusible ions such as carbonates, sulphates, sodium, calcium, phosphorus, potassium, iodine and others, allow the fish absorb them through their gills tissue or skin.   But the main set back is the high loss of potency of most water soluble vitamins in aquarium water -- some as high as 60% within 24 hours.

Oil soluble vitamins( A,E,D,K) and insoluble minerals (copper, magnesium, iron, and most trace elements) will precipitate when diluted in water even when the best formulated solvents are used.  Thus you can see that the best way to feed your fish with vitamins and minerals is to incorporate them into a prepared diet and feed the fish regularly.  The amount of vitamins and minerals required to vitalizes your fish in liquid form is impractical and costly.  Imagine pouring liquid vitamins and mineral into the ocean or even in an open cage in marine fish farming -- and expect good results!

Aquarium fish should be fed regularly and in moderation. Feed at least twice a day and each time with as much food as they can consume in a few minutes.  In a community tank make sure that the bottom feeders are not left without food because other feeders might have taken all the food before it sinks to the bottom.  If you happen to keep a special type of fish, make sure you know what type of food it prefers otherwise it may starve to death.
Do not overfeed.  The uneaten food will decay in the aquarium and cause pollution and fouling of the tank.
Back to Page 1


Keep a sharp look out for abnormal behavior among fishes during the first feed in the morning.

(1)      Look around the tank or pond for dead fish.  If they are found check for cause of death:

(2)       During feeding, the fish all rush for food.  Look out for: (3)      Check for fishes that are externally off-colour and different from the most healthy specimens.
(4)  If you noticed that the fishes are not as active and lively as on other days, but they all seems to be normal in
      general appearance.  Then something may be wrong with the quality of aquarium water. Check temperature,
      pH, hardness, ammonia and nitrite contents.  Whatever the test results, it is always better to change at least
      25% of water in case some toxic substances have entered the aquarium from unknown origin (insecticide
      spray, cat's and dog's urine etc.).  USE RID-ALL ANTI-CHORINE AND GENERAL AID immediately after
      change of water.
Back to Page 1 


The diseases of Aquarium fish from marine, cold and tropical waters species, are as complicated as those from the human beings. Very little research has been done on the aquarium fish diseases by dedicated ornamental fish culturists, veterinary scientists or fish-health professionals except by a few fish enthusiasts or hobbyists who happened to be doctors from the medical profession.

Fortunately, during the last few years, there has been an increase in countries like Norway, Greece, Chile, Canada, UK, Denmark, Austria, Sweden, Finland, Korea, USA and Iceland.  They have extensive investments in the aquaculture industries with emphasis on food fish farming in controlled water ways and marine cages and pens.  Diseases in caged fish are more prevalent than in the open sea.  Therefore, for the food fish farmers, lack of positive control over health and diet problems from fry to adult stages of their fish will result in delayed harvesting and thus lower profits or even loss of income.  The food fish rearing projects and hatcheries are hundreds of time more than those of the ornamental fish industries.

Let us hope that we will soon be able to benefit from these food fish farmers’ research in fish diseases as they started to breed food fish from eggs to adult fish the way we breed our aquarium fish.  We must remember that poor or inadequate environmental conditions induce stress and cause ill health and most disease problems.
The following are the main causes of fish diseases in aquarium fish:

Any item from the above cause diseases in most aquarium fishes. The hobbyist should remember that there are plenty of  pathogenic bacteria, parasites, fungi etc. waiting to invade and attack your fishes the moment their immunological defense systems are not up to par.

Back to Page 1


Preventive treatment is extremely important for fish heath.  Prevent the above ten environmental problems and you will find your aquarium fish facing very little health crisis.  If your fish fall sick they may be treated by three major  routes of drug administration - in-feed or in-water medications and  by injections.


To make in-feed medication for ornamental fish, mix flake food, pellets or minced prawns with the drugs (usually antibiotic drugs or drugs that are almost insoluble in water) and solidify in warm agar or gelatin which is allowed to cool off before using as medicated feeds.


For in-water treatment of aquarium fishes the chemicals or drugs are added to the water for use as a bath, flush, a dip or as a prolonged bath.


For big fishes like Koi, “Big-sized” Goldfish, Arrowanas, cichlids, you may consider using injections.  I would suggest, as a lay hobbyist, you should leave this to the veterinary surgeons or the professionals.

For aquarium fish there are three main methods of injections: (1) Intraperitoneal or IP, (2) Intramuscular or IM,  and  (3) Dorsal sinus.  A small gauge needle such as the 25GA or less is required.

In Singapore, you need a poison license to buy controlled drugs and one to store them.  Most injections are antibiotics or sulpha drugs and they are mostly classified as scheduled poisons (under the Poisons Act) in Singapore.  These regulations make injecting sick fish a real professional matter!

General identification of common fish diseases

As aquarium fish hobbyists we will only identify fish diseases by their visual signs in colour or growth (if any) on the diseased fish body and fins.  The behaviour of the diseased fish will also be taken  into consideration.

We leave the definitive identification procedures of diseases by using  the microscope and waiting for the bacteria cell growth to appear on culture media to the experts. After all, not all fish hobbyists own high power microscope or facilities to prepare culture media. To simplify the procedures in diagnosis and treatment of diseases, we separate them into the following groups:

( A ) Diseases caused by bacterial infections

Bacteria occur everywhere and come in various forms.  They can be shaped like sphere, rod, or spiral and arranged singly in clusters or chains. They are very numerous and most are useful to humans and fishes.
They are responsible for the decay of dead plants and animals, a continuous process which releases nutrients to be recycled repeatedly.  In the aquatic environment, the result  of  bacterial activities are responsible for the nitrification process, whereby the ammonia and nitrites are converted to the less harmful nitrates in the biological systems.   Bacteria are always present in aquarium water but those which causes outbreaks of fish diseases occur only when the fishes are kept in unsuitable conditions such as deteriorated water quality.  Bacteria that cause diseases or problems in aquarium water are known as “pathogenic” bacteria.  Many pathogenic bacteria live with our fishes and us.  We will never totally get rid of them in our aquariums or ponds; we can only control and contain them.

The main bacterial diseases in Aquarium fishes are:

FURUNCULOSIS - a very infectious diseases caused by Aeromonas Salmonicida. Affects mainly trout, salmons and ulcer diseases of Koi and goldfishes.  There are rod-shaped short gram-negative bacteria measuring about 2 microns.  The pathogens are transmitted through infected fish, skin parasites. Poor water quality foster a wider spread of the diseases.

DIAGNOSIS:  External signs are swollen abdomen, redness at the base of fins, in the mouth, in the grooves under the lower jaw, gill cover and around the anus and sometime the body wall are covered with boils and lesions as big as long as 20 mm.  These lesions will develop into ulcers in some species, such as carps and Kois.

In Kois, the ulcers will further develop into Carp Erythrodermatitis, a skin disease which will quickly lead to secondary fungal infections or invade the body leading to internal lesions and septicemia.

The affected fish usually looks lethargic,  darker in colour.  It loses appetite, stays at side of aquarium or pond and remains near the surface and is occasionally swept to downstream where there is less water disturbance. Internal organs and body tissues are also inflamed.


There is no low cost effective treatment for this disease.  If the fishes are cheap, destroy the whole lot, disinfect all the utensils, equipment, tanks and ponds with calcium hydroxide for one week before restarting your new stock.  If you have expensive fish such as Koi or some rare species, then you will have to try to save them.
The cheapest drug to use are the sulpha drugs such as combination of sulphamerazine (0.20g/kg of fish per day for 7 days) and  sulphaguanidine (0.10g/kg of fish per day for  seven days) powders incorporated into feeds for controlled feeding of sick fishes.  Oxytetracyclines ( 55 mg. per kg. of fish per day for 10 days) and Furazolidone (35 mg per kg. weight of fish per day for 20 days or more) are most commonly used in feed to treat affected fish except that the latter is known to be carcinogenic and banned for use in food fish farms.
Potentiated sulfonamides such as Tribressen (1mg/kg of fish per day for two weeks) are effective against Furunculosis therapeutically, but the cost is very high.  Oxolinic Acid (5mg/kg of fish per day for 10 days), Furazolidone (35mg./kg of fish per day for 14 days), Nitrofurazone (75 mg/kg of fish per day for 14 days ) and Oxytetracycline (55 mg/kg of fish per day for 10 days) have been prescribed frequently as additive to feed affected fish in their medicinal diet with good results.

Some Koi  breeders claimed to use Powders of Azactam  Gentamycin,  Kanamycin, and  Augmentin with great results! - but I believe that their wallets become very much lighter even before they can see any real result.  Alternatively, all fishes with external lesions or visible injuries must be dipped in undiluted RID-ALL ANTI FUNGUS for at least 5 minutes before placing them in the bath of the same medication of 5 ml. to 10 litres for big fish or 25 litres for small fish for about 3 days, then add in more medication for another week until the ulcer area begins to turn white.

If your fishes are mainly goldfish or Koi, then bath in RID-ALL KOI AND GOLDFISH SPECIAL instead.

COLUMNARIS INFECTION  (Tail and Finrot, Peduncle Diseases, Saddleback, "Cotton Wool" Diseases, Black Patch Necrosis, Haemorrhagic and Ulcer Disease) mainly caused by Flexibacter columnaris and various types of bacteria such as Aeromonas, Pseudomonas, and Cytophaga (myxobacteria).
Water with too high pH value and high temperatures, oxygen depletion, water contaminated  with faecal matter,  poor water quality poorly maintained aquariums or ponds and acute stress can encourage the disease.

COLUMNARIS is primarily an epithelial disease.  It causes erosive and necrotic skin and gill lesions that may become systemic.  It often appears as whitish plaques (or thick mucus) with red periphery on the head, percula and fins especially around the caudal fin.

Fragments of the fin rays may remain after the epithelium has sloughed leaving a ragged appearance (fin rot).
Lesions rapidly progress to ulcers usually within 24 hours, which may be yellow or orange due to masses of pigmented bacteria.   Lesions may also form black patches on body, fin and back (black patch necrosis).

The body, in severe cases may become bloated or swollen in some areas.  Ulceration spread by radial expansion may penetrate into deeper tissues producing a bacteremia (haemorrhagic septicemia and ulcer) and with external fungus growth (cotton wool diseases).

Columnaris gill infection are less common but with high mortality because of impaired gill filaments and tissues due to infections.

Peduncle Diseases are caused by several species of Cytophoga psychrophilus formally known as myxobacteria..  If the bacteria invaded the fins causing necrosis of  tissue and confine to the fins alone is called fin rot disease, but when the necrosis enters tissue at the base of the caudal fin or peduncle it is called the peduncle diseases.

The treatment  regime for the above group of bacteria diseases are the same.


Antibiotics such as Oxytetracycline hydrochloride  (100 mg per litre as prolonged bath daily for 3 days), and Neomycin sulphate (250mg. per 100 g feed every four hour for three days) or use 50mg/litre of water as long bath for at least three days), are effective treatment.

For prolonged immersion, use nifurpirinol 0.1mg. per litre and treat for 4 or 5 days.  Alternatively non-antibiotics treatments are also as effective.

Dilute RID-ALL COPPER AID from 5 ml. to 15 litres.  Dipped the affected fish in the final solution for about 5 to 10 minutes, before transferring them to another tank for a long bath with normal dose of RID-ALL ANTI FUNGUS for at least three days.


EGG FUNGUS AND FISH FUNGUS - Fish and Egg Fungus are caused by various species of aquatic fungi such as Saprolegnia and Achlya.  There are thousands of fungi in the aquatic world and most are saprophytes, feeding on dead organic matter. Some are parasites of animals and plants  and some are important source of antibiotics   such as Penicillin.  Popular types of fungi are the yeast and mushrooms.  Another type of fungal diseases affecting gill tissue, is known as Branchiomycosis.  It attacks mainly guppies.

DIAGNOSIS: A Cotton Wool-like growth or tufts on damaged skins and fins of fishes.   Generally the fish might have already suffered from other forms of  infections (ich, ulcers etc.) which caused the mucus layer to become damaged.

Fungus will then attack the damaged area forming the well known thin white threads known as the fungal mat or mycelium.  Large amount of  fungus  and fungal spores are always abundant where there is plenty of decaying organic matter.  As a result,  the moment there is a dead fish egg available,  the spores will settle on the dead egg and the fungi grow rapidly to spread to the  adjacent healthy eggs killing the whole lot.
Some fungi developing on or in gill tissue penetrates blood vessels which cause the gill to appear bright red from impaired circulation.  These groups of Branchiomycosis fungi produce spores attach to the gill, germinate and produce hyphae which penetrate gills epithelium.  The infected fish may be weak and lethargic with respiratory distress and sudden deaths are common.  The dead fish usually has bright red gills and if the pH of the water is acidic the mortality rate could reach 50%.


Fungi are very infectious but fortunately, they attack only damaged area or lesions caused by other diseases.  They are usually secondary infections caused by insufficient care given to a series of serious bacteria infections or physical damage.  The natural layer of undamaged mucus that covers the healthy fish is the best protection against fungus attack.  There are many effective remedies available for the treatment of fungus infection.  Most antibiotics (use same dosage as in bacterial infections) can be used against fungus but not as effective as against bacteria.

Rid-All Anti fungus at a dose of 5 ml. to 25 litres kills most fungi in the aquarium environment.  For better and quicker results remove the white threads or white mat with a twister and apply the damaged area with undiluted Anti fungus before the general  treatment.

(C) Parasites

There are thousands of various types of parasites  infecting the aquarium fishes.  Protozoan ectoparasites are the most common parasites encountered in aquarium and cultured fish.  This group is a diverse array of mainly ciliates and flagellates that feed on the most superficial skin layer, known as the epithelium.
Most feed only on the epithelium's surface, while some, (e.g. Ich)   penetrate into the epithelium.  The feeding activities  cause serious visual damage to the hosts.  One of the most common damages caused by the parasites are a reactive hyperplasia of the epithelium and an increase in mucus production.
When the hyperplasia is severe, it appears as a white cyst or peppered with white dots and cloudiness to the skin. The same problems can occur on the gills and leads to hypoxia (insufficient oxygen intake).
All protozoan ectoparasites have a direct life cycle and reproduce faster at higher temperature.  Generation time of some species may be as little as 24 hours under favourable conditions.  This will quickly overwhelm a host population.
Effective treatment of these parasites depends on an understanding of the two major types of life styles:  nonencysting and encysting.
Another type of parasites are living worms in the internal organs of the host especially the intestines, swim bladders, peritoneal cavities and even the gonads. Most of them have a very complicated life cycle.

Nonencysting Protozoan – Attached to gills, fins, in muscle tissue and on skins (e.g., Trichodina, Ichthyobodo or Costia necatrix) and complete their life cycle on the host and are easily treated, usually with a single short - term drug application. However if the infections are found in the internal organs, the treatment can be difficult and unpredictable.

Encysting Protozoan – The feeding stage feeds in a nodule formed in the skin or gill epithelium and when mature they break through the epithelium, falls off the host and form an encapsulated diving stage known as tomont which secretes a sticky capsule.
These  reproductive capsules adhere to plants, nets, ornaments and any object found in the aquarium.
They multiply by binary infusion and within 8 to 24 hour, large numbers of new swamer cells are formed. They then break through the nodules (or cyst) and actively swim for a new host fish.
The reproductive cysts (e.g., Ichthyophthirus,   Amyloodinium) are resistant to treatment, so therapy must be directed at the free swimming, infective stage.
This requires that drugs and chemicals be present for a longer period or requires several treatments be applied to ensure that all infective stages are destroyed.

DIAGNOSIS:   There are more than 60,000 known types of parasites, which affect the health of living things on earth.  Several types of parasites also plague aquarium fish, which makes fish keeping a real nuisance.  We will deal with some of these which are commonly encountered by the Aquarius.

Unicellular (Protozoa):

CHILODINELLA – infects gill mostly - whitish or bluish sheen on body, “tattered” appearance to skin - feed by penetrating the host cells or directly on epithelium - advance infestations cause skin ulcers, sliminess of the skin and secondary bacterial infections and death.
TRICHODINA – High mortality if  infects small and baby fishes - attacks marine and freshwater fish - infest both skin and gills - fish rub and scratch themselves against rocks and plants or jerk violently with their fins.
COSTIA – also known as Ichthyobodo necatrix  - White-Coat diseases - bluish or whitish film on body – penetrates, the epithelium causing tissue irritation.  Also leads to epithelial hyperplasia and increase mucus production.
ICHTHYOPHTHIRIUS  MUTIFILIIS (White sport diseases – Ich) – The most common diseases of fresh water fish.  Virtually all  freshwater fish are susceptible this infection, although scale less fish, such as catfish and loaches are especially vulnerable with possible 100% mortality rate.  They appear as white cysts or salt-like dusting on the skin, fin and gills.  A common temperature for ich outbreaks is 150 C to 250 C and complete their life cycle in 3 to 6 days.
OODINIUM – MARINE (amyloodinium) and FRESHWATER (piscinoodinium)  (red -velvet diseases) – Both diseases have golden, dust-like sheen (velvet) on skin.  The life cycle is the same as for Ich but completed in 10 to 14 days under optimal condition.
GILL FLUKES  (Dactylogyrus)  –  an nonogenean infection which attack mainly  the superficial layers of the gills and cause the fish to suffer dyspnea and hypoxia.
SKIN FLUKES (Gyrodactylus) – another common nonogenean infection, but this disease causes cloudiness to skin, grey-white caste or irregular areas on skin, eroded fin, focal hemorrhages on skin, and incite excess mucus production or pruritus.
FLAGELLATE PROTOZOA – (Hexamita or Hole-In-The-Head Disease) – This disease mostly affects cichlids such as Angelfish, Discus, Oscars, large South American Cichlids and even Gouramis.

Almost all known information regarding this disease are based on popular aquarium literature and there are no published scientific reports.  Some aquarium experts believe that the diseases are caused by a mineral imbalance that results in skeletal damage leading to the pitting lesions.  Some claim that the disease is due to the lack of vitamin C in normal diet.

Some speculate that heavy concentration of flagellates in the intestine can cause maladsorption, leading to the mineral imbalance.

Another hypothesis is that a Hexamita-like flagellate, which is present as a latent intestinal infection, spreads by both extension and hematogenously to the gall bladder, peritoneal cavity, spleen, kidney, and associated vasculature.  In later stages,  the hole-in-the-head lesions appear, first as pin point lesions that may discharge small,  white  short “threads” of material containing the parasites and looks like white worm.  The pin point lesions become bigger as time goes on and may be as big as several millimeters across.  Secondary infections such as bacteria and fungi may set in and the ultimate cause of death may be secondary microbial infections.

2. Complex Parasites:

These Groups Of Parasites attack the host either externally or internally or both.  Most are introduced into the aquarium from wild or pond-raised fish and mostly from live food such as tubifex worms and live plants.
We only look into a few that commonly affect the freshwater aquarium keepers.

EXTERNAL PARASITES LICE ( Argulus) – A saucer shaped crustacean which affects mostly Koi and gold fish.
Attack by inserting a pre-oral sting (stylet) into the host and sucking body fluid or blood with its sucker mouth.  Fish display violent erratic swimming and other abnormal behavior because of the skin damage caused by the repeated piercing of the skin by the stylet which injects toxic enzymes, causing irritation.  Focal red lesion and focal darkening of colour on skin.

ANCHOR WORM (Lernae) – A lernacid copepod that possesses anchor-like processes for securing themselves to the host.  Koi, Goldfish and carps are most commonly affected.  Various sized (from barely visible to about 10 mm) copepods attached to oral cavity, gill arches, or skin; erosion or ulceration; red area on skin, may be raised up to 5 mm in height.

LEECHES – A parasitic species of annelids having a complete digestive tract with a
mouth in the anterior sucker  and an anus in the  posterior suckers. They  are hematophagous and suck blood even during the night.  Hosts  usually suffered severe chronic anemia, small red or white lesions on skin and some can cause large ulcers on skin and in the mouth.

TAPEWORMS (CESTODES) – Usually appear as white, elongated, tangled piece of segmented ribbon-like string and may grow up to several centimetres long.  In the case of heavy infestations the fish may become emaciated with heavy worm burdens with some parasite protruding from the vent.  By then the adult worm may have already infested the peritoneal cavity, liver, or muscle and the intestine, which may become obstructed or perforated.

ROUNDWORM (NEMATODE) – The adult forms are normally found in the digestive tract where some can cause chronic wasting if present in high numbers.  Heavy infestation emaciates the host, producing a sharp ridge under the dorsal skin.  The adult  worms’ bodies  are thin, unsegmented, round, spindle shaped or thread-like cross-section.

PINWORMS or TREADWORMS (OXYURIDA) – These worms, experts claimed affects only the discus.  They feed on the intestinal contents and damage the host by depriving nourishment from them.  The host becomes timid, darkens and finally wastes away.


Luckily for the fish hobbyist, the treatment procedure for most parasite infections in this classification is all the same:

  1. If the parasites are visible ,first remove them carefully with a surgical forceps.  Pull out slowly but some may still  have their head embedded in the epithelium.  Dab the affected area with undiluted Rid-All Anti-Fungus or lotion Potassium permanganate 1:1000
  2. Use Rid-All Copper Aid at normal dosage for one day.  Add Rid-All Anti-Ich on the next day.  On the 3rd day displace 25% water and add Copper Aid and Anti Ich together at normal dosage of 5 ml to 25 litres for both types. Keep a good look out on the 4th day and 5th day.  If there is sign of improvement repeat the procedure on the 6th day.  If there is no improvement at all, change to one of the following treatments.
  3. Malachite Green 0.75% in formalin 40%.  Use 2 drops for five litres as bath for 3  days.
  4. Most effective treatment for nonencysted nematodes – Levamisole Hydrochloride at the dose of 10 mg per litre for prolonged immersion.
  5. The best treatment is to use a pesticide or insecticide known as Dimilin manufactured by Union Carbide Company also known as Diofluorobenzuron.  Usually one dose of 1 gm in 1000 Gallons of water is more than enough to kill all Lice and Anchor worm in one single prolonged bath.  Unfortunately you may need a permit to use it.
  6. Another popularly used Insecticide is an Organophosphorous known as Trichlorfon or Masoten or Dipterex.   Same dosage as Dimilin but much more toxic to fish and the applicator.  When added to water Trichlorfon degrades to the more toxic Dichlorvos (DDVP).  Both can cause neurotoxic poisoning in humans. So avoid inhalation or absorption through the skin.  This item is available from flowers and nurseries shops.  The liquid form is very unstable and if the solvent is water, the potency is less than one week. If the powder looks wet, lumpy or translucent it has degraded to the toxic Dichlorvos and should not be used. Therefore if you buy a liquid form of Trichlorfon make sure you buy a reputable products such as the Neguvon (an 8% Trichlorfon in a specially prepared solution) otherwise you are wasting your  money and time.  This item may also need permit to use in some countries.

The most efficient way to treat internal parasites is  to feed the fish orally with the drugs.
The following drugs are used in order of my preference for all known internal parasites

Back to Page 1


Effective treatment of diseases for all things on earth depends on accurate diagnosis of the diseases and the correct usage of the best drugs and chemicals available at that point of time.   Most drug failure in treating fish diseases is due to improper diagnosis.  Since fish don't talk or complain, most diagnosis are based on external observations and their behaviours.  Very few hobbyists will send their fish for pathological tests before giving them any medical treatment.

In the aquarium trade there are many drugs and chemicals used in the treatment of aquarium fish diseases.  Unfortunately most of the scientifically proven treatments are based on work with food fish. There is much information that purports the efficacy of many drugs and chemical formulations for treating aquarium fish diseases, but most lack  reliable scientific data supporting their use.  Most of over-the–counter products are based on the so-called established formulations by the few aquarium fish experts.

Some products are poorly formulated with poor quality pharmaceuticals.  Instead of helping the aquarium enthusiasts to treat their sick fish, they destroy the fish.  This will indirectly discourage the fish hobbyists (especially the new enthusiasts) from pursuing their new interest.  The aquarium trade may also lose a large number of potential customers.

Most of the defects in the formulation of aquarium pharmaceuticals by some over-the- counter aquarium remedies manufacturers arise from the use of substandard raw materials – maybe intentionally to reduce cost. For example: a kilogram of Methylene blue technical grade (used in the tanning and paint manufacturing industries) cost only S$16.00 while one kilogram of Methylene blue B.P.C.(British Pharmaceutical Codex) for medicinal purposes cost about S$100.00!  Another chemical is the Formalin.  The commercial grade is cheaper by almost 30% as compared to the pharmaceutical grade

I have seen Methylene blue Technical Grade packed in 1 kg. plastic containers. The content was plainly labeled as Methylene Blue without stating the qualities or standards with an address of a German Chemical Company as manufacturer. It was being sold at a value meant for medicinal purposes.

If the use of aquarium pharmaceutical, or over-the-counter remedies is required, be sure to purchase them from reliable sources.  Always insist on U.S.P. or B.P. or B.P.C. or their Veterinary grades and qualities.  State clearly the type you required - water soluble or insoluble.  Don’t waste money on the wrong grade of drug.
Unfortunately, some aquarium shops will recommend items which will bring in the most profits for them. The best quality products are not recommended because they usually have a much lower profit margin.

The following drugs and chemicals are commonly used in the aquarium fish culture.  For general information, their dosage, qualities and standards are given as a guide.  Dosages as far as possible are given within a range, since accurate dosage depends on water and environmental conditions.

For in-water treatment, water quality can greatly affect efficacy and ichthyotoxicity.  Related pathogens can also vary in susceptibility.

If you are not sure of the dosage, always start with the lower dosage.  If the disease does not respond adequately, repeat the treatment with a higher dose.  Always look out for adverse reactions.  For oral medication, dosage varies with feed intake.  Make a higher concentration of drug in the feed if the fish eats less.   If the fish is unable to eat use a soluble drug for in-water treatment.

ACRIFLAVINE  B.P.C. – Also known as TYPAFLAVIN, NEUTROFLAVINE, GONOCRINE, OR PANFLAVINE.  A  group of quinoline antimicrobial dyes structurally related to acridine.  Hydrochloride salts are normally used because it is more stable in aqueous form.  Bacteriostatic against many Gram-positive bacteria but less effective against Gram-negative bacteria.  Not effective against spores.  Use for early stages of fungal, bacterial infections and infestations of the diseases.  Very effective for external wounds and cuts.  Use 0.01% as preventive and 0.03% for treatment.

MALACHITE GREEN is a diarymethane dye, which  is the most effective agent for treating water mold infections of fish and eggs.  Also effective against protozoan ectoparasites.  Toxic to some fishes such as fries or baby fish,  tetras, catfish, and loaches.  Be careful and watch out for adverse reactions when treating fish without scales. There are many grades of Malachite green in the market. Make sure you use only the Zinc Free oxalate grade.  Use 0.1 mg per litre for prolonged immersion and 100 mg per litre as swab to skin lesions.

METHYLENE BLUE – An effective agent for treating and preventing bacterial and fungal infections of freshwater fish eggs and for treating ectoparasites of fresh water fish.  Use 2 mg. per litre of water and repeat on alternate days for up to 3 times.  Use the pharmaceutical or B.P.C. grade.

METRONIDAZOLE (Flagyl) – An effective treatment for hexamitosis, spironuleosis and some bacterial infections since the 1970’s.  I normally use the injections (200 mg/ 25 ml. In vial form.) for prolonged immersion at the dose of 20 mg. per litre (i.e. 1 vial for use in 10 litres of water).  Add 1 vial every day for three day before stopping treatment.  It is more efficient to use as feed if the fish will consume food.  For feed use 100 mg. per kilo of body weight.

FORMALIN – An aqueous solution of 37% to 40% formaldehyde gases.  Formalin is volatile and irritating with a very pungent odour.  The commercial grade has darker colour and sometimes with brownish precipitates.  The  better B.P. grade is more stable and the liquid is practically colourless.  As a prolonged immersion in aquarium use, 0.015 ml to 0.025 ml per litre every other day, for three days.  For one-hour bath, use 0.125 ml to 0.250 ml per litre.


These wide range of pharmaceuticals are mainly used for the treatment of bacteria diseases of aquarium fish.  This group of drugs, also known as antibacterial agents, is highly abused in their uses, both therapeutically and prophylactically, by the aquarium industries.  All antibiotics when used therapeutically must be for at least 3 days even if the diseases seem to have disappeared or cured.  The prophylactic use of antibiotics should be discouraged as it is the main cause of a high prevalence of multiple antibiotic-resistant bacteria in aquarium fish.  It is not wise to start your fish on antibiotic therapy without knowing the causative agent (i.e. the type of bacteria ).   However, because it is difficult to pin point the causes of most bacterial diseases in aquarium fish without elaborate laboratory tests, most aquarists will just use any type of antibiotic available.  Fish treated with antibiotics should be monitored closely to ensure that the treatment is effective and complete.

Dosage of antibiotics depends largely on severity of diseases and tolerance of the particular species.  There is no fixed dosage and generally one capsule or tablet meant for human may be used in 1 litre to 5 litres depending on type of fish and severity of their problems  Generally, if the antibiotics are insoluble in water it is better to use in-feed method of administration while the soluble type are more appropriate for in-water treatment.

AMOXYCILLIN and its salt Trihydrate are insoluble in water.  Use 50 to 80 mg. per kilo of body weight as feed for 10 days.  Amoxycillin sodium are the soluble salt and more suitable for in water treatment.  Use 250 mg. to 1 to 5 litres of water.

AMPICILLIN and its salt Trihydrate are insoluble in water, use as feed.  Use the soluble Sodium salt for in-water treatment.  Both dosage are the same as Amoxycillin.

CHLORAMPHENICAL is the drug of choice  for abdominal dropsy and gold fish ulcer diseases caused by Aeromonas Salmonicida.  Very unstable in liquid form but the Chloramphenical Sodium Succinate at the dosage of 40 mg. per litre are poorly absorbed but stable in water for slightly more than 20 hours.  More suitable for use as  injection at the dosage level of 20 to 50 mg. per kilo of body weight once weekly for two weeks.  For Feed use 500 mg. per 100 gram of feed and feed twice daily for 3 days.

CHLOTETRACYCLINE, OXYTETRACYCLINE, and TETRACYCLINE are the most commonly used tetracycline groups of drugs   Use their water soluble  Hydrochloride salts for in-water treatment and make sure that your aquarium water is slightly acidic for best results.  It is better to use the pure powder than from the capsules  which are meant for human use.

Most capsules contain lactose, starch  or even sugar as inert ingredients but these are not suitable for aquarium use.  If water changes to brownish or reddish colour, replace at least 25 %; or better still change to a new tank to avoid adverse reactions.

Dosage for prolonged immersions: 20 to 100 mg. per litre of water for at least 3 days.   As feed, the Oxytetracycline (Terramycin) are preferred at the dosage of 50 to 80 mg. per kilo of body weight for 10 days.

ERYTHROMYCIN and its groups are mostly insoluble in water and as oral feed they have very bitter taste.  They are not suitable to use for prolonged immersion.  The Erythromycin Phosphate or Thiocyanate has been used as feed for food fish at the dose of 100 mg. per kilo of body weight for 10 days.

NEOMYCIN SULPHATE an aminoglycoside antibiotic used for topical administration to damaged skin, open wounds and also infected cavities.  Dosage for prolonged immersion is 50 mg. per litre of water every 3 days for 9 days.  Cross-sensitivity with other aminoglycoside may occur.



These Nitrofurans are an effective group of synthetic antimicrobials.  Some are stable in both fresh and salt water and are rapidly absorbed by fish.  They are effective against many of the common pathogens that affect fish.  A single bath treatment is often effective against susceptible organisms.  Suitable for use as feed and as prolonged bath.

Unfortunately, Nitrofurans are carcinogenic, genotoxic, and mutagenic and are strictly illegal for use in many countries, including United States and Japan.  But the Japanese are exporting the products packed in beautiful 5 gram silver-foiled packings to other Asian Counties like Singapore, Thailand and Malaysia.  The most unfortunate thing is that some aquarium shops introduce these products as a cure – for all fish problems with total disregard for the safety of the people using them.


OXOLINIC ACID –  A popular quinolone, a class of synthetic antimicrobials that are effective against many gram-negative bacterial pathogens of fish.  They are well absorbed orally and can be bacteriostatic or bactericidal.  Oral formulations: 10 mg. per kilo of body weight for 10 days.  For prolonged immersion use 1 mg. per litre for 24 hours.

FLUMEQUINE –  structurally related to Oxolinic Acid and Nalidixic acid and are used for the same purposes.  Dosage:  As feed, use 10 mg. to 1 kilo of body weight for 10 days.  For immersion use 5 to 10 mg. per litre.  Maintain pH between 6.5  to 7.5.   Use higher dosage for marine water.

NALIDIXIC ACID – another  quinolones – more suitable to use as a bath at the dosage of 10 to 15 mg. per litre for 1 to 4 hours.

SARAFLOXACIN – claimed to be the latest addition to the fluoroquinolone family.  Has broad-spectrum potency against many fish pathogens and are being investigated by several commercial fish hatcheries.


SULFAMETHOXAZOL – TRIMETHROPIM (Bactrium) – The most popular Sulpha drug used in the aquarium trade.  Used mainly as feed at the rate of 10 mg. per kilo of body weight for 10 days.  Most drugs in this class are toxic to fish while some are virtually useless because of widespread resistance.


These are series of non-pathogenic, dorman or sporulated (not freeze dried) bacteria specially designed to overcome a variety of aquaria waste problems.  A specially designed synergistic combination of bacteria such as Bacillus Subtilis, B. Licheniformis, B. Polymyxa, Pseudomonas Aeruginosa, P. Putida, P. Fluorescens, and Escherichia Hermannii are used to degrade organic matter.  The other two species of popular nitrifying bacteria  (Nitrosomonas, Nitrobacter) are used for ammonia removal.  They are effective only if used correctly.  Their shelf-life is about 6 months if properly stored.

Back to Page 1


The above formulations and aquarium pharmaceuticals are  short listed from a pool of thousands of items available to the hobbyist, professional aquaculturists and even more for the Doctors who are also fish hobbyists.
Most medications are available over-the–counter in aquarium stores and aquaculture supply firms, including antibiotics that are usually only available by prescription for ethical veterinary use.  Always look for expiry date before purchase.

The availability of these products varies from country to country.  In Singapore, most drugs, whether for humans or for veterinary purposes, are controlled by the Poisons Acts.

Please remember that there are no short-cuts to good fish-keeping by using drugs and pharmaceuticals.  It is very naïve to think that using the latest and most expensive antibiotics or drugs will keep your fish healthy and happy.  The same goes for algae in the aquarium.  If you don't control the source of the problem (amount of light entering the aquarium) but prefer to use algaecide instead, then, you must source for the unobtainable type of algaecide that is non-toxic to fish for long-term immersions.


The above articles are mainly base on my personal experiences gathered from my 35 years of working with the aquarium fish, they are exclusively for the readers’ information only.  All the treatment methods, procedures and dosages are frequently used for treating fish in my own aquariums.  Most dosages and treatments used are based on practical experience and from information gathered from medical journals, aquarium books and even the extra pharmacopoeia – martindale.
All information are given in good faith and from personal experience.
The correct usage of drugs and their recommended treatment methods when adopted or used by the readers are beyond our direct control.  It has been proven beyond any reasonable doubt that different species of fish react differently to the same drug even under the same environmental conditions.
Users are expected to check their compatibility under prevailing conditions in the aquarium environment.
Hong Tai Aquarium Products Private Limited and myself cannot be held responsible or to accept liabilities in the use of pharmaceuticals and their suggested treatment procedures.

We welcome any constructive suggestion to improve this website.

Phillips Tan
25th November 1997

Frequently Asked Questions (FAQ)
Tips on Fish Keeping

World Yellow PagesWorld Yellow Pages