Fish inevitably get sick. While frequent illnesses are probably a sign of poor maintenance, all aquariums eventually have problems. Pathogens come from a variety of places, but usually from either new fish or unfiltered tap water. Treating fish illnesses can seem like a black art. There are many medications on the market, most of which seem to kill the fish they were trying to save.

The most important thing to remember is: don't kill your biological filter! Never add antibiotic tablets directly to the tank water. If the fish will eat, use an antibiotic food such as Tetra Medica. Avoid overfeeding so as little of the food goes into your filters as possible.

Unfortunately most sick fish won't eat. Instead, place the fish in a 5 gallon bucket or tank with a small heater and airstone. Medicate the water in the bucket. Change the water every 1-2 days by throwing out the old water, replacing it with water from the tank and adding new medication. Not only is this safer for the remaining healthy fish in the tank, but it also water changes the tank, reducing toxins which may have precipitated the disease. I prefer this method over normal hospital tanks because extra tanks are a pain to maintain and their biofilters are constantly killed by medications. Buy a 5 or 10 gallon tank or bucket, heater and airpump, and use it when you need it!

Whenever more than one fish becomes ill or if you believe your water quality is poor, always perform a series of small water changes. Change 5-10% of the water once a day for 3-6 days. You should avoid large water changes because fish become accustomed to accumulated toxins in the water. Removing those toxins suddenly can shock the fish and make them more sick! Instead, you should gradually improve the water quality over several days. Many tank problems will clear up after several small water changes.

Treating fish illnesses is difficult because many illnesses look alike. Picking the correct medication for the pathogen is critical to success. Below are some tips for curing common fish diseases.


(lots of tiny white spots)

Ich is the easiest disease to recognize because of the distinctive white spots it creates. This disease is caused by a parasite, so the first step in curing it is to raise the tank temperature by a couple degrees. This accelerates the life cycle of the organism so all the eggs will hatch before you stop treating the tank! You can also fight ich by adding an additional 1 tablespoon of salt for every 10 gallons or raising the PH. Most parasites and fungus are more sensitive to salinity and PH changes than fish. If these "natural" steps don't fix the problem, treat the tank with a ich medication as directed. These medications won't kill your biofilter.

Bacterial and Fungal Fin Rot

(white film or fuzz on fins and scales)

Fin rot diseases form a film or fuzz on the fins and scales of the fish, slowly dissolving the fish's protective slime coating and eventually the fins themselves! These symptoms can be caused by both bacterial and fungal pathogens. The best cure I've found is Jungle Fungus Eliminator. This chemical attacks both bacteria and fungus and is safe to add directly to the tank if all the fish are affected. However, if only a couple fish are sick, I recommend treating in a bucket.

Internal Bacterial Infections

(red spots or swim bladder problems)

Internal bacterial infections are a job for antibiotics or antibacterial chemicals. Symptoms include red streaks on the fins and tail, disorientation and listing due to swim bladder infection, and rapid serial death (if all the fish are rapidly dying, you should check your water quality). If the fish will eat, use antibiotic food, otherwise treat with an antibiotic or Jungle Fungus Eliminator in a bucket or small tank. These diseases can have very few symptoms and cause very rapid death. If one fish gets sick, watch the others closely for symptoms!

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Last modified at Sunday, April 19, 2015