We have had our male Betta for about a year and a half. He recently became lethargic, did not eat and his fins were literally coming apart (like shedding or molting). I changed his water but there seemed to be no change and his fins continually "fell apart." After about 4 or 5 days he just snapped out of it, ate well, was active and normal. His fins are now shorter but seem in good condition. What happened? And should I expect it to happen again or periodically? If not, is there something we should or should not do to avoid it in the future? We use distilled water in his tank of about 3/4 gallon size, but in my online research I have read not to use distilled. Why not, and since he has been doing well with it for so long should we just continue with it?