goldfish sick or not

Question
hi, this is Jackie, from Calamesa. i have a fish tank with about 10 goldfish and one bottom feeder and to day when i looked in the tank i noticed that some of the goldfish had brown spots on them are my fish sick or what? please reply I'm really worried.

Answer
Hi Jackie;

Make a 25% water change and have the water tested. Sometimes dark spots on goldfish are from ammonia (NH3) or nitrite (NO2) burns. Those toxins can rise from "New Tank Syndrome", overcrowding, overcleaning that disturbs the biological balance, overfeeding, etc. If you can tell me what size your tank is, how big the fish are, how long it has been set up, type of filter, etc., I can help you figure it out.

At Your Service;
Chris Robbins