It sounds like the fins have ammonia burn from the uncycled tank. Naturals I have kept during a cycle have had the same problem in the past. Too many fish added too fast. Do frequent water changes.
Could also be a problem with your transport. I just helped a friend set up a 90 gal. In addition to what I gave him, he had caught some crappie. I noticed that they all had what looked like fin rot on the cadual/pect fin(s). Turns out it was the bucket he was transporting them in. He lost both in his Q-tank.
Ok, Ive been trying to keep crappie in my tank and so far have been rather unsucessful. Ive got one thats doing great but Ive had 4 die on me. The ones that died all had fin rot or some other infection that I could not cure. Do you guys put something in the water you keep your fish in? Like something to reduce stress.
Something I've learned recently: treat your transport water with non-iodized salt (kosher salt, aquarium salt) and also treat your QT with 1-2 tbsp per 5 gallons. I also use stress coat or novaqua whichever I have handy in addition to the salt. Have melafix handy, but the salt will help prevent the fin rot in the first place and slow it down if it occurs. If you start to see it, treat with melafix and hope that it fixes it.
It sounds like the fins have ammonia burn from the uncycled tank. Naturals I have kept during a cycle have had the same problem in the past. Too many fish added too fast. Do frequent water changes.
I agree with Drewish. Your problem is due to transport. I used to have similar problems, but started adding salt to the collection bucket as he desribes and all but eliminated any finrot. In fact I keep all of my tanks salted at all times. 1 tablespoon per 5 gallons.
I also use Jungle bag buddies for transport.