Diseases in Tropical Fish

Aquarium Illness Facts and Aquarium Care

When keeping any animal in captivity, the health and well-being of the animal becomes the responsibility of the owner. When an animal becomes sick, it can be difficult to diagnose the problem accurately, as many of the procedures used in modern medicine are not available for animals, or are prohibitively expensive. However, there are things that a fish owner can do to prevent disease and to keep his fish healthy.

Most disease organisms that can affect pet fish are already present in all but the newest aquariums. The majority of these bacteria, fungi, protists, and other microscopic parasites (called pathogens) can travel by air for great distances. Some can even survive long droughts, so a long-dry, used aquarium may not be free of disease organisms! If these pathogens are in everybody's aquariums all the time, you might ask, then, why aren't everybody's fish always sick? People's fish aren't always sick because most healthy fish can fight off the common pathogens with their immune system. The biggest factor in keeping your aquarium disease-free is to keep the fish healthy.

To keep your fish healthy, your best bet is to keep them in a healthy, low stress environment. More than 80% of disease outbreaks in an aquarium can be traced to failure on one or more of these issues. To keep your tank healthy:

• Perform regular, small water changes to remove any unprocessed waste and to remove any decaying organic matter (primarily from excess feeding and dead leaves or roots from plants). I recommend 10-15% of the aquarium volume be changed once a week. This also helps prevent the build-up of minerals or toxins in the water as water evaporates and dust and debris settle into the tank.
• When you do the water change, be sure to vacuum part of the gravel to remove any debris collecting unseen in the spaces between the rocks. You may not be able to see this debris, but it can make a significant impact on the quality of the water, and therefore on your fish's health.
• Provide the proper maintenance for your filter, including changing filter cartridges, cleaning media, and cleaning and maintaining pumps. A poorly maintained filter cannot do its job.
• Keep your aquarium at the correct temperature for the fish. Fish that are kept in water that is significantly too warm or too cold, or even fish that are kept slightly too warm or cold for long periods of time are going to be stressed and this will repress their immune systems.
• Provide your fish with a well-decorated tank to help reduce stress. Most fish do better in tanks with 50-75% cover - plenty of hiding places, so your fish rarely feel exposed and threatened.
• Keep the population density in your aquarium low to relieve stress, avoid aggression, and improve your fish's overall health. Overpopulated tanks will have lower oxygen content in the water, higher waste content, and otherwise poorer water quality.
• Provide your fish with a proper, balanced diet and a variety of foods. Also, don't overfeed your fish. Providing more food than the fish will consume readily will contribute to poor water quality.
• Avoid transporting your fish. Any time you move a fish, it is stressful, and you will weaken the fish's immune system for a short time. As a rule of thumb, the longer the fish was in transit, the more stressed it is and the longer it will take to recover. For this reason, it is recommended that any new additions to your aquarium be quarantined in a hospital tank before being introduced to your general population.
• Be conservative with medications. Almost all medications are stressful to both your fish and your filter, so medicating when not necessary can actually increase your fish's chances of contracting something, so only medicate when necessary.
• Monitor your tank for signs of aggression. A fish that is being beat up and chased around is going to be more stressed than one that is peacefully getting along with its tank mates.

Remember, a stressed fish has a repressed immune system, and a fish with a repressed immune system will not be as able to resist a disease as a healthy fish.

In addition, there are some things that will increase your fish's risk of disease. Once a fish becomes sick, the population of disease organisms in the tank increases, and the health of the pathogens also increases. This makes it harder for other fish to resist the disease. For this reason, it is important to remove any sick fish to a hospital tank as soon as you can see signs of ill health. At this point, it is a good idea to see if you can figure out what caused your fish to become susceptible. Check the points above for some ideas. Also, if a fish dies in your tank, it is important to remove the body immediately. Not only is the body of the deceased fish contributing to poor water quality by decaying in the tank, but a fish's chance of contracting a disease is many times higher if it eats a fish that was already infected - or worse yet, one that died from the disease!

Water from unknown sources can also be dangerous. Any water from another tank is a potential risk to your fish. When you add water from someone else's tank, you do not really know what pathogens are available in the water and in what population. You do not know if the fish in the tank were about to come down with something or had just gotten over something. Any of these conditions can contribute to an increased pathogen population which could overwhelm your fish's immune system.

Remember to keep a close eye on your fish. Most diseases are much easier to treat if you catch them in the early stages. Should your fish become sick, there are many medications on the market that will quickly and accurately treat most of the diseases your fish are likely to encounter.

My snail mail address is: Keith Seyffarth, 217 W. Koch, #308, Bozeman, MT 59715.
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Page most recently modified: November 26 2006 18:05:55.