Tail falling off?

[Letitluce]

I'm very concerned - part of my axolotl's tail seems to have fallen away! Could this be at the fault of his tank mate? (Another axolotl) I don't expect it is because I have never seen any kind of violence or even innocent nibbling between them. Any suggestions on what could be wrong?
Also, asides from that, he seems perfectly healthy.

 

[HayleyK]

Is there anything else sharp in the tank? Filter inlets? What are your parameters?

If everything is in check then it most likely was the other tank mate. How often & what do you feed them? Nipping is usually due to hungriness. Occassionally they can nip without reason but it's not that common.

 

[Letitluce]

There is a filter, which I actually did initially suspect. I'll place it higher up. I feed them every night and Paulo (the one who I'm concerned about) is always a much more enthusiastic eater than his tank mate Ringo. Thank you for the feedback!