Sounds to me that you may have a case of Camellanus Worms. For your sake I hope not. But sounds to me like thats what you have. If your fish sits still for a little while see if you can see tiny red hair-like worms sticking out of the fish's vent area. If you do then your fish has Camellanus. Good news is, you will get a bunch of people on here tell you what you can use to treat it. Bad news is, chances are you will find yourself on the internet looking all over the world for the chemicals and come up empty handed. Now!!!!!! You can go grab Jungle Anti-Parisite Medicated Fish Food from ur local pet store. But in most cases your fish will only eat it 1 time. Which isnt very helpful because they need to eat it for at least 3 days out of a week, for 4 weeks. I had to go to the store and buy raw shrimp and mix the fish food with the shrimp. Grind the food down to a powder and crush the shrimp into a slime/liquid. (almost like you chewed it up and spit it out). Mix the fishfood and the shrimp together to make a dough. Roll it in a thin long line. Let it sit in the fridge for about an hour. Then cut it into small pieces and try to feed it to them like that. Its the only way I can think how to do it. I am treating all my fish for this problem AS WE SPEAK. This is the only route I can take since nobody knows where to locate these other "remedys". You'll notice that alot of people on here will just give you the name of something to get, but they wont know where to get it. It will get frustrating. But if you do have Camellanus (which I hope u dont). You will find urself resorting to my post's advice since nobody else will give you anything useful. They'll give you the name of something to use, but wont tell you where to get it, or how much to dose the tank. Well, im spent. Good luck, and I hope this helps.