Understanding fish diseases and how to prevent them from happening.

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Does anyone have the time?
Sep 12, 2004
Gulfport, MS
I have seen a lot of posts saying things like: help I think I got ick, what is this, etc. So here is an article which will hopefully help you get a better understanding of disease and prevention, and how to diagnose what your fish has.

Preventing disease:

The health of your fish depends on the quality of thier enviroment. Poor water conditions, stress, and/or incorrect feeding can cause illness, therefore it is up to you to see that this doesn't happen. Certain procedures must be taken to prevent diseases from making themeselves at home on your fish. Quarantine new species that will be introduced into your tank so you can evaluate them thoroughly. Keep in mind to handle your fish correctly when moving them whether it be from a bag or from another tank. Prevent poisons from predators from entering your tank. Make sure that heating, lighting, air, and filtration is functioning properly and well maintained. Last thing to do is make sure that the water quality is fresh, clean, and balanced for your fish. Also, if you have a planted aquarium don't forget to care for them as well.


Quarantining new fish can help stop spreading possible diseases. You can monitor the fishes behaivor. Spot diseases, if any, and treat according to the type of disease. I recommend you keep new fish quaratined for 2-3 weeks before introducing them to a community tank.

Reducing stress:

Stress is a major factor in preventing disease. It is caused by bad handling, poor water conditions, sudden changes in water conditions, and the famous tapping on the glass. If you have to move a fish, remember to handle with care, if you are rough it will cause the fish to stress out. Light changes will cause fish to be stressed, to soften this shock follow this procedure:

Switch off the aquarium light before turning off the lights in the room, wait about 5-15 minutes so the fish can get adjusted to the low light level, then turn off the room lights.

A stressed out fishes immune systems is lowered, therefore allowing infections and disease to occur.


If you use a net to move a sick fish keep in mind that net is now contagious and should not be used until disinfected. You should be able to pick up a disinfecting solution at your local fish store.


Overfeeding your fish can cause algal and bacteria growth so make sure you feed your fish accordingly. A common cause of low immune systems in fish is a lack of vitamins. To prevent this use a variety of foods as like you and me, I'm sure that fish get tired of eating the same thing day after day.

Types of ailments:

External infections are easily seen and treated. Internal disorders, however are much harder to determine and cure.


These are the creatures that make homes out of our fish and are very much unwelcome. Most parasites feed primarily on the mucus layer on the skin and gills. Larger parasites penetrate the skin and feed on blood and tissue.

Bacteria and fungae:

Basically this is caused by poor tank conditions. Dead plant matter, feces, and/or uneaten food encourage bacteria or fungae to grow.

Skin disorders:

This is the most common problem found in fishes. They are caused by bacteria or parasites. There are several symptoms involved in diagnosing a skin disorder which I will explain in another article.

Gill disorders:

Basically it is when the fish have problems with thier respiratory system. In time the gills will thicken up in response to the chronic irritation. This can and will slowly suffocate the fish. The cause of this condition may be slime disease, gill flukes, or bacterial damage.

Disorder of the eyes:

Many of the same diseases that affect a fishes skin can also affect its eyes. Bad handling and/or poor water conditions cause minimal damage which will allow bacteria or fungae infections to occur.


This is when the fish appears to be abnormally swollen. They often can't be distinguished from each other without a post-mortem.


Weight loss resulting in an uneven appearance. This is caused by harassment of an individual fish preventing access to food, or a disease such as tuberculosis, which is more common.

Swim bladder problem:

Abnormal swimming or difficulty maintaining equilibrium may be due to several reasons:

Deformed swim bladder
Cancer or tuberculosis in organ next to the swim bladder
Poor nutrition
Chilling (colder water)
Serious parasitic infestation
Serious bacterial infections

If you think your fish has a swim bladder problem check and treat for other diseases first.

Well, I hope that this article has been very helpfull and informative. Good luck to all of you in preventing diseases. Look for my next article within the next few days on different diseases and how to eradicate them.
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