Unfortunately, even the most dedicated aquarist will from time to time have an outbreak of disease in the aquariums. How you handle these situations may be critical to your success as a hobbyist. One of the most common mistakes aquarists make is to medicate too soon. Very often the fish will fight off the disease on its own, provided that its immunity system is strong. I rarely medicate an aquarium. Rather, I rely on a series of partial water changes to rid the aquarium of parasites, pathogens, and other disease causing organisms. What follows are some of the diseases you are likely to run into and my recommended treatment. Please be aware that this is from my personal experience.
Ich (White Spot)
This is a parasite which resembles grains of salt on your fish. At first the white spots are small, usually present within the gills of the fish. Your fish may breath heavily or scratch against decorations in an attempt to remove the parasite. Within a day or two the parasites will have grown and multiplied, covering the body of the fish with tiny white spots. There are many techniques available to fight off Ich. The most common involves using copper sulfate, which kills free swimming parasites. Copper is very effective but can be stressful for your fish, especially scaleless fish. Copper can also have a negative effect on your biological filter bed, if your tank is not very well established. It is also not healthy for your live plants. A good alternative is to use Malachite Green. Malachite Green is commonly sold in pet stores, usually in combination with Formalin. Some common medications include Noxich and QuickCure. I have had excellent luck with both of these products. You should still use precaution when treating tetras or scaleless fish, although these products are safe with Live Plants. The usual recommendation is to treat at 1/2 dose for sensitive fish. Another method for treating Ich which can be useful is to slowly raise the temperature of your aquarium to a little above 29°C. This will dramatically speed up the life cycle of the parasite, driving it out of the system. However, this method relies on your fishes immunity system to fight the disease. Many hobbyists also advocate the use of salt to fight off Ich. They recommend adding 1 teaspoon of salt to 4 liters (1 gallon) of water. This will effectively irritate the skin of the fish, causing them to produce and excessive amount of slime. The slime coat serves as a protective layer to fight off parasites. I personally do not believe in this technique or any technique which causes unnecessary stress on the fish. There are other techniques available which are just as effective.
This is also a parasite, but is luckily not as common as Ich. Velvet appears as a rust colored parasite which is very small and often difficult to see. It is usually clustered very heavily on the fish, forming sort of a rust colored blanket. Velvet attacks your fish very quickly and could even wipe out a tank in a matter of 2 days. To be honest, I have not come across an effective treatment. If I had an outbreak I would attempt adding salt and using copper in combination with Malachite Green. I would also raise the temperature and do a 90% water change. Good luck.
A fungal infection appears as a white cotton growth on the body or fins of the fish. The majority of white spots you see on your fish are going to be parasites. In the slim chance that you have a fungal infection then I would recommend not treating at all. A true fungal infection is practically harmless to your fish and should be attacked successfully by your fish's immunity system.
These usually appear as red patches or streaks on the body of the fish, or sometimes appear as damage to the fins of the fish, such as "fin rot". Bacterial infections are almost always due to poor, declining water conditions. This does not necessarily have to be high levels of ammonia, nitrite, or nitrate. Lack of regular water changes will result in increased numbers of pathogens and other disease-causing organisms which thrive in neglected aquariums. Bacterial infections are also commonly associated with parasite infection, as a secondary infection. I rarely recommend medicating for a bacterial infection as a series of partial water changes can usually eliminate the problem. Medicating can also have an adverse effect on your biological filter, as medications will not distinguish the good bacteria from the bad.
Prevent Rather Than Treat!
All in all, the majority of infections can be eliminated or prevented by frequent partial water changes, and ensuring that your fish lives in an appropriate environment (tank size, tank mates, etc) and water quality. Medications are rarely needed and should be avoided whenever possible.
Note: recent posts on Aqualink have revealed that Malachite Green increases in toxicity to fish as the temperature increases. You may want to reconsider your decision to use Malachite Green if you intend to raise the temperature at the same time, or if you already maintain your temperature at a higher level than normal. For the record, I have not personally experienced this problem.
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