Common Tropical Fish Diseases and Treatments

Fish diseases are as common as those found in other animals and can have several causes.

One of the main factors that contribute significantly to fish disease is the lowering of the immune system through stress.

Stress is caused primarily by poor water quality but also by other factors such as overcrowding, bullying, or failing to acclimatize new fish.

Table of Contents

Common Tropical Fish Diseases
Common Tropical Fish Treatments

Common Tropical Fish Diseases

Fish diseases are divided into two categories, parasitic and bacterial.

Parasitic Infection – Often comes from the introduction of new fish that are carrying parasites.

Otherwise, a small population of parasites residing in an aquarium are held in check by the resident fishes’ immune system but can take hold if fish become stressed and susceptible.

Bacterial Infection – This can also be caused by stress or carried by fish but can also be a secondary effect of a parasitic infection.

Let’s take a look at the most common tropical fish diseases:-

Whitespot

Whitespot or Ich is probably the most common form of a parasitic infection. Easily spotted by the large number of tiny white spots that appear on the fish.

It normally first appears on the fins but will quickly spread all over the body and can be fatal if the gills are infected. It will spread throughout the tank if untreated.

Whitespot is largely stress-related and can result from a change in water temperature, poor water quality, or overcrowding. It can easily be introduced from outside so be sure to check any new fish for signs before adding them to the aquarium.

The parasite that causes Whitespot, Ichthyophthirius multifiliis, can be weakened by raising the water temperature to 30 C (86F), which stops it from completing its life cycle.

Otherwise, Whitespot can be easily cured, if caught early enough, by using an anti-whitespot treatment (see below).

Pop Eye

Pop eye can be diagnosed by one or both of a fish’s eyes protruding abnormally.

It can be caused by several factors but will only rarely spread to other fish in the aquarium.

It can go away on its own or you can apply a specially formulated pop eye treatment (see below).

Dropsy

Dropsy is a bacterial infection that significantly changes a fish’s appearance as they swell up with fluid to the point where scales are raised and the eyes protrude.

It is usually associated with poor water conditions and can be fatal.

Dropsy is difficult to treat but can be cured by moving the fish to a hospital tank and adding aquarium salt at 1 tsp per gallon.

A broad spectrum antibiotic should also be added such as Octozin (see below).

Fin Rot

Fin rot is caused by bacteria that are always present in aquarium water but fish will only become susceptible in poor water conditions such as those found in unfiltered small tanks and bowls.

Treat with an anti-fungal treatment (see below).

Fungus

Fungus is caused by fungal spores present in aquarium water and is often caused by damage to a fish due to poor handling or aggressive tank mates.

Treat with an anti-fungal treatment (see below) as soon as the problem is spotted or it can penetrate deep into the fish and prove fatal.

Lice

Fish lice are ugly external parasites that are fairly easy to spot. They can be removed by hand but it’s more practical to use a specially formulated treatment to kill both the lice and their eggs (see below).

Common Tropical Fish Treatments

Tip: Many fish diseases are avoidable by practicing good fish husbandry, regular water changes, filter maintenance, etc and good feeding with the best tropical fish foods.

It may also be a good idea to have a spare aquarium ready that you can use to set up as a hospital or quarantine tank.

Not only can it be used to treat sick fish, but it can be useful for quarantining new fish until you are satisfied they are 100% healthy.

See our article, How to Set Up a Quarantine Fish Tank for more information.

The following specially formulated treatments will deal with most fish diseases:-

Note: Be sure to follow any instructions carefully and do not overdose. You may also need to remove any activated carbon during treatment as this will absorb some or all of the active ingredients of the medication.

Whitespot and Fungus

Dropsy

Pop Eye and Fin Rot

Lice