I noticed my 24"+ RTC having small portions missing from his tail, looks like they've been bitten off in a skirmish. Tankmates are 26"+ Asian RTC, 20" CK, and a 18" pleco.
Tail Damage in RTC
- Thread starter Hartzell
- Start date
I would say any of the mentioned fish could be the culprit. I keep some cichlids, and some basic community fish with 2 small RTC's in my 265 and every now and then they get nipped up. My little 4" black shark chases my 8" TSN all over. Its only a matter of time until he realizes he can easily EAT the shark 
bob
bob
keep an eye on the barbells(whiskers), for erosion. If the barbells start to erode and the fins start to get smaller and smaller with bone possibly showing, then your fish might have a desiese known as fin and tail rot otherwise your tankmates are probably picking on him. Fin and tail rot affects most catfish especially pimelodids. You would be amazed at how fast they can lose their fins, tail, and barbells due to this desiese. It is easily treatable. Good luck and keep us updated. Got any pics of the damage?