Tropical Fish Diseases

There are quite a few tropical fish diseases out there, and too many cures to go into everyone of them in a a single post here at the Novice Aquarist.  Personally, I prefer to prevent disease by removing the various causes that can contribute to an outbreak.  One of the least used, but most effective is the quarantine aquarium where all new fish should be kept for at least a week to ensure they are not carrying any problems from the old tank to the new.

It is my personal belief that most fish (as most other animals) are all subclinically ill to one degree or another.  They are carrying quite a few of the common diseases found to attack them, but they are healthy enough to withstand them.  Stresses placed on your fish are usually the reason that an illness is able to take hold.  A stable and constant temperature is required for good health.  Fluctuation temperatures, even as little as a couple of degrees in a 24 hour period can cause ICH to appear.  Other diseases may also be a result of drastic changes in temperature as well.  Other problems can become evident when the water characteristics are poor, or ammonia and nitrite are in the water.

The topic is so vast and confusing, entire websites are devoted to identifying and treating the various types of problems that fish may display.  I break the problems into a few different categories:

  • Toxins
  • Parasites
  • Fungus
  • Bacteria
  • Viruses

Toxins – Often the fish will poison themselves with their own production of ammonia and nitrite in a new aquarium, or where the beneficial bacterial populations are deficient to remove them immediately.  Overpopulation can also be a grave problem, especially when starting a new tank.  It is important to understand the Nitrogen Cycle and Biological Filtration to understand the way these toxins must be controlled.

Parasites – Probably the greatest amount of problems are created by attacks of parasites onto the fish. These have life cycles that must be considered when treating them, since in most cases when you see the disease, it is invulnerable to medication, only in later stages will it be able to be killed – usually in a free swimming stage. The two most common pests are ICH and Oodinium.

Fungus – Fungus can grow on either the fish directly or on surfaces in the tank where the proper hygiene has not ignored.  In most cases the cure is a combination of medicine and tank maintenance.

Bacteria – Bacteria can either be beneficial or pathogenic.  The good ones remove toxins and provide proper water for the fish to survive.  Pathogens can attack the fish with devastating results.  The problem with many of them it that the antibiotics may not always work.  It is important to properly diagnose the fish disease before the medication is selected

Virus – Viral infections are known in fish, and they are almost impossible to treat, antibiotics do not seem to be effective.  In these case, often it is best to euthanize the fish rather than spend a lot of money on ineffective treatments and endanger the entire tank at the same time.

Tropical Fish Diseases – A good reference site

I don’t rely on memory when treating any of the many tropical fish disease.  I refer to the various sites devoted to identification and treatment of problems.  I, of course have my favorite remedies, and also very few problems because I try to remove the causes before they become clinical.  Using Nutrafin Cycle on a regular basis ensures the right bacteria are there, and that pathogens have serious problems gaining a foothold.

When I find myself in doubt as to what I am dealing with, or want a second opinion, I use the Fish Disease Diagnostic Tool at Their extensive list of tropical fish diseases and the acknowledged treatments fo them will help you diagnose, treat and save fish that are having health problems. But the best start to any treatment is the segregate any diseased fish into a quarantine tank and reduce the chances of infection throughout the entire aquarium.


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