Sick Neon Tetra

Question
My tank has been set up for about fifteen years. It holds 10 gallons of water. The afflicted fish is a Neon Tetra. I have about fifteen small fish. My filter is an Aqua Clear with a carbon filter, a sponge, and some sort of clay filter. I'm not sure what the levels are. I change the water monthly, and I replace a third to a half of the water each time.

One of my neon tetras has a large white tumor-looking protrusion on the base of his tail. It has developed in the last couple of days. He has been swimming fine and still eats but I'm not sure what to do.

Answer
Hi Alex;

So sorry it took so long for me to get back to you. It's been very busy around here.

It's hard to say what it could be. Tumor and abscess are possibilities, as well as a cyst. There isn't much you can do though, especially in a fish so small. You could treat with an antibiotic in case it's being caused by a bacterial infection. I would isolate him first though. You don't want to just put medication in the whole tank because it really makes a mess and fish that aren't sick should not be treated. A good antibiotic to try would be "Maracyn Two". It's available at most fish stores.

I hope he does okay...

At Your Service;
Chris Robbins