If i get a black ghost knife fish will he eat his tankmates. Will there be room for him. I am planning on having him in my 55 with 2 yellow labs and 2 psuedotropheus zebra ( don't know common name. They each get like 5" Is this big enought? Also i want an unidentified 7" Plec. I have been watching him at the LFs and he hasn't grown any in like a month.