I just set up a Rubbermaid 100 gallon stock tank for feeders. I put an Aquaclear 110, which was already running on a 55 gallon for 2 years, and a 6" air stone on it. I put 100 Fathead minnows in from a local breeder. For the last week the minnows get this white covering in patches on their tails and head and then die. My water tests 0 Ammonia, 0 Nitrites and 0 Nitrates. I put 1 tsp/gallon of salt in the tank and have treated with Pimafix and Melafix with no success. Anyone know what I'm dealing with or what I'm doing wrong? I had this happen last year when I had them in a established 55 with good water parameters too- I just thought it was too small a tank for 100 minnows. But now the same thing in a bigger tank. I know 100 gallons is too small for 100 fish, but there isn't 100 fish in there very long as I'm feeding 15 every other day. Any help would be appreciated.