I have a CT male and he has a pretty big lump on his tail. It looks almost like a bubble, I'm not sure if it's hard or not. It seems to be slowly getting bigger. He eats and acts normally so I'm not too concerned about it. I'm just curious as to what it is.
He's just under a year old and is in a 5.5 gallon tank (divided in 2), it IS cycled with a heater at 78C. He is otherwise very healthy and active. I will try and post a picture but I have to figure out how to post it from my phone so give me a few minutes!