From that picture, the upper tail looks split, but it is still hard to see. Is that what he looked like when you got him? If not, do you have sharp decorations? How big is your tank and as bahamut285 said do you have a heater?
And thanks for that picture, I had no idea they existed!
Kindness and respect should be shown to all animals, no matter if they are furry, scaly, big, or small. Be a hero to the animals and GO VEGAN!