blisters/lumps

Question
I have a 55 gallon tank with a 75 gallon filter with a comet, koi, and fantail and i have started to see a growth on both the comet and koi.  I just recently added the koi and about a week later i have started seeing the growth.  The color of the growth is dependant on the color of the fish.  My white koi has multiple white growths on its fins and the comet has a rather large growth on its tailfin...if you could help me diagnose their ailment i would greatly appreciate it.

Answer
Hi Alex;

I would suspect lymphocystis or "carp pox". They are both viruses. Lympho looks like little bunches of cauliflower, pox lesions look waxy. There is no cure for either one but water quality improvement can control them. Replace 25% of the water at least once a week. Get a test kit to measure the levels of ammonia, nitrite and nitrate so you know the water change schedule is helping enough for the fish to have strong immune systems. If the new koi brought it into your tank, the stress of having been moved to new home probably caused it to show itself. Or, the added level of wastes stressed your other fish too and one of them had it to pass on to the others. These illnesses are much like herpes in humans. It doesn't usually kill and is always in the infected person's body and not contagious at that time, but when the body is stressed, the disease shows it's symptoms and spreads to others.

With the koi in there this may be a losing battle for you though. Those guys get about 3 feet long and really need a minimum of a 500 gallon tank or pond. The problem now is that if he indeed has a virus, you won't be able to find a home for him unless the new owner's fish are infected as well. Otherwise, it will be spread to others. It's a tough decision for sure.

Let me know what the growths look like (waxy, cauliflower or something else) and we can go from there...

At Your Service;
Chris Robbins