Unless frogfish are special, I don't think his tail will grow back much if at all. My experience with chomped tails is that if its below the caudal peduncle (the area where the fin joins to the meaty part containing the backbone) it won't grow back like it was before. It may just be a stump. My understanding is that frogfish don't really use their tail much anyways so I don't think this will be a problem.
However I could also be talking out of my arse on this so just to cover mine in case his tail grows back fully, I'll mention that in case I look like a doofus later on
