Fish sick

Question
I have 5 fish in an 18 gallon tank. Had them for 6 months. There is an under rock filter and the hood has a filer.The fish are 2 pacosamis, 1 bleeding heart tetra, 1 black tetra, and 1 fan tail gold fish. (a big fantail goldfish). I use to have another fantail goldfish but it was dead this morning. And now the bigger goldfish has white stuff on his tail and body. What is wrong with him and what can I do to fix it?

Answer
Hi Lee-Ann;

That's a shame. I'm sorry you lost one. Let's see if we can save the second one......

Their trouble may be the result of the goldfish being kept long-term with tropicals. They can't tolerate the high temperatures. Goldfish really should be in a cool water tank. Fantails are easily picked on too because they are slower than most tropicals. The tetras you have are especially good at picking on slower and/or docile fish. They can be very quick and do it when you don't see them. I've had it happen to me too. Tetras are also schooling fish and should be in threes or more of the same kind. It makes them happier and less determined to bother other fish.

I would put the goldfish in his own tank with a good power filter (no heater) and hopefully he will do better. For large goldfish, a 20 gallon is the minimum size. Also add aquarium salt to his tank. A dose of 1/2 teaspoon per gallon is good. Add the same dose for every gallon of water you change each week. Just being in new water will be helpful for him too. The salt helps him fight infection and strengthens his slime coating. Another thing you can use is Melafix by Aquarium Pharmaceuticals. Along with the salt they are a great infection fighting team without stressing the fish like regular medicines do.

It is also possible that the tank needs more cleaning. Goldfish are deep-bodied fish that produce a lot of waste. If they are especially large, they are going to produce even more than their share for a tank that size. Make 25% water changes every week while vacuuming the gravel. This will help everyone stay healthy.

Followups welcome

At Your Service;
Chris Robbins

Come on over and join us on the freshwater fish forum at About.com to get even more information too;
http://freshaquarium.about.com/od/questionsanswers/a/naavigateforum.htm

My member name is ChrisR62. See You There!