at mt local pet store there is a clown knife that is around 8 in but is in a 10 gallon tank. i dont have my 500 gallon ready for fish but my dad has a 90 gallon. in his tank he has two 8in tinfoil barbs, two bichirs and some small cichlids and catfish. do you think that i could by the knife and put it in the 90 gallon. i hate seeing a fish in such bad living conditions.plus there only selling it for 12 dollars, and yes it looks healthy.