I don't know the history of the fish but my guess is bad water and a 10-20gal tank, but my fish store buddy called me and told me he just got a RTC and royal clown knife that some guy did not want anymore. When I got there I noticed the RTC had gills that curled. Has anyone ever messed with it. He's about 8" long and the RCK is about 10". I put them in the 125gal with aquarium salt to try to get the stress levels down. Are they going to stay curled or will they go straight? Do they usually come through it ok? I don't no anything about gill curl except what I already looked up on the computer, and I trust you all more with info being you all have been there and done that (so to speak).