Water levels are all okay, the fish itself seems okay at times, I have 5 barbs which came with the tank i bought so i dont know how old they are and i have had them for a couple of months now. This barb does hide a few hours a day in its cave, but except that it swims around happily. The only disease i have seen and treated before was white spot and that was years ago... i did assume a bite at first but i dont have any fish that could do that except its own species. I have Guppies, bristlenose plecs, sucking loach, mollies, tetra...