yes, if it happened in a short period of time, like overnight or in a few hours - he very well may be tail bitting. They bite for several reasons - Anger, Bored, or just because they can. Did anything in his home change? if not, try rearranging his tank, he may just be bored. SOmetimes longer finned ones like VT and HM bite because their tails are too big/heavy...not sure about CT's though. If he is doing it just because he can - nothing you can do about it. Its kinda like humans nail bitting. The best thing is to keep his water super clean, and warm. Stress coat can help with fin regrowth but only if he stops bitting.
The hole in his tail my be a bit mark. Normally they start out as a small U shape.
Also - how often and how much do you change the water. Ammonia can also burn their fins off if the level is high enough.
Fin rot will have a black outline around the infected area, usually.
Last edited by Tikibirds; 04-26-2012 at 07:02 PM.