goldfish attacked!

Question
Hi,

Background Information: My sucker fish attacked my pearl scale goldfish leaving her without "pearls" on one side, showing just bare skin. We have removed the sucker fish from the tank. This had happened to one of our other pearl scale fish a few days before, although we didn't know the problem and we had put in tetracycline as that was recommended by a pet store. That was Friday night. The first fish had died and then this other fish started showing the same symptoms on Sunday night. Some of her pearls which are still there are white and swollen, but seemed to have decreased in swelling since Sunday. The pet store told us to put malafix in the tank, which we have been doing daily since Sunday. Tuesday when I came home the water was a dark brown red color and my fish had fuzzy stuff growing on her. I called the pet store and they suggested it could be from the two medications combining. I did a water change, and then gave the daily dose of malafix. Today the water was again brown, and there is a layer of bubbles on the top, I have just did another water change.

General information: we have 6 fish in the tank, the water stays about 23'C it is a 25 gallon tank and the ammonia and nitrate etc are all good

Questions:
What is the fuzzy stuff?
Would the malafix change my water color and make the bubbles in the water?
Should I use something else to treat my fish and should I separate her from the others?

Thanks for your time (if you need pictures just ask and I can email you some)


Answer
ok... sucker fish ... usually only attack fish out of desperation... I would make sure it is getting enough food to eat... supplement its diet with algae wafers. There is usually not enough food in tanks to support sucker fish and thus their diets should always be supplemented.  How much Malafix are you putting in the tank?  Did you do water changes between medication does??? The fuzzy stuff is probably fungus.  let me know... dave