I need help diagnosing my fish. Two of my fish, a rainbowfish and a platy, have large, broad white patches on their tail fins. Pictures are below, but some additional information that might help:
-two days ago, a seemingly healthy, new rainbowfish died suddenly. It had no white patches, although it was being bullied by the dominant male rainbow.
-this is a new tank about 2-3 weeks old. It's in a Silent Cycle so ammonia and nitrite are, and have been, zero. Other parameters look good.
-The first fish I put in the tank were five rainbowfish from a LFS that was not reputable (big mistake). Of the five, only one has survived. The ones that died also had sudden white patches on their fins. I suspected it was Velvet, but I'm not sure.
-The currently infected fish show no other symptoms- no dashing against rocks or labored breathing. The white patches appeared quite suddenly (nearly overnight).
-The other fish (5 cories, 6 ottos, and two new rainbows) are seemingly unaffected and show no patches of white.
Here are pictures ...
