Why in gods name would you keep an Aba with a wolf fish?
Is he still housed with the wolf fish?
Why should it matter too much if it's kept with anything at all?
I mean, it isn't common to see an Aba-Aba live with anything. But it has been done. So I'd just be happy if his case was the same as those who've made it work (As in, the comm was maintained for a prolonged period of time).

Tail including bone being bitten off = making it work
As you will, anyway.

(At best. At worst, well.....)it looks like some of the bone has been taken off there - dont think its going to grow back perfectly. might be a little odd looking.....