I think you should invest the thirty bucks in some test kits. If your water quality is poor, you could very well find yourself in the same situation in a day or two, because the fish are still in that same water. Often, one fish is more susceptible to disease or illness than another, and so he will begin to show symptoms, but then the next-susceptible will also begin to show them, etc. So, just because only this fish seemed to be affected doesn't mean that there's nothing wrong with your water. It would still be wise to take the time to answer all of the questions that Lupin stated in his post, and to be as specific as possible, so that if there is a problem, you can get it taken care of before you lose another fish.
