I keep goldfish from my pond successfully all winter in a 48 gallon tank. It was cleaned out for the summer, but I recently set it up with a 5" Crappie, some snails and crayfish. The Crappie has developed a pink fuzzy spot above the front fin and behind the head. It could have been from an injury when it was taken from the lake. Since my husband wants to keep this type of fresh water fish for the winter, I wanted to know what to treat or cure it with if it happens again. The tank temp is 75 degrees. The pH is 7.6, the nitrite is 0, ammonia is 1.0. I will also post in the Ponds forum.