sick goldfish. what should i do

Question
Hi,
I have a very sick looking goldfish and I really dont want it to die!
I have a tank with four fish. Two comets and two male sword tails. One of the comets is not eating. Last night it was hanging around the top corners near the surface. Today it is hanging around the bottom in the corners on its left had side. It cannot swim straight, When it tries it does summersaults. The week before this happened it was looking a bit bloated but it isnt so much now. I have had the fish for a year with no problems. I feed them vegetarian flakes and there is a filter and plants in the tank. As well as a snail. I change the water once a month, about a third of it and the tank does not look dirty although there is debris among the stones at the bottom that I cannot get out. The other three fish are absolutely fine...
What should I do?

Answer
Amelia,
Before addressing your sick goldfish, I must tell you, there is another problem with your tank. Comets are a cold water fish and sword tails require a heater set at 82 degrees!! You must separate these fish and purchase another tank and a heater. Your goldfish is suffering from swim bladder. Here is a remedy:

Swim Bladder Disease
First you must fast your goldfish for 2 days. Cook a frozen pea, remove the outer shell and throw it away. The outer shell cannot be digested by your fish! Cut the cooked pea into tiny pieces. Feed this to your fish. Fast him for another 2 days. If that doesn't work, cook another pea and feed it to him again. After he's had the second pea, fast him again for 2 more days. This should cure him of swim bladder.

All fish require their water tested and a 25% water change every week. Clear water is not a sign of good water quality, please do not be fooled by this! As far as the debris among the stones at the bottom, I suggest you buy a gravel vacuum. Also it is very important to remove any uneaten food from the tank after feeding. Water quality is the main reason fish get sick and die.

It is important to research your fish before you buy them so you can have happy healthy fish. I hope this helps.