I bought 15 H. Rasboras all at once thinking it would be better to get a school instead of one at a time. They reside in my 55g along with a male betta, 2 sunset dwarf gouramis, 4 mystery snails and a spotted raphael cat. I have 2 HOB filters running full blast with a combined flow rate of 530 gph. I've had the school for about 3 weeks now and every week (not including the first week) I will find two of the rasboras have something white and fluffy on their chin and their body color fades. The first time I saw this I took in the pair and spoke to the LFS. He advised me to do the 50% water change twice a week and add Stability and the rest should be fine. Today I find two more fish with the same symptoms and most of the school has stopped swimming back and forth. I've removed the fish but I need to know how to stop this from killing off my entire school. None of the other fish seem to be affected.