I had a small octopus a lion fish and a snowflake eel in the same tank. It was a 55G with 3 decorative corals. (this was before live rock and corals were popular) The octopus left the fish alone (which was much bigger than him) but bugged the crap out of the eel, also I had some crabs that had buried themselves in the sand they were gonners immediately. After he lost a leg to the eel he left him alone. If ignorance is bliss than I got lucky. I had an acrylic tank with openings on the top, he new they were there he just never got out. Maybe because I had the water level lower; the water line was about an inch or more down from the top, I don't know. I never had them covered and he never escaped. I wouldn't say they are strictly bottom dwellers. He would chase feeder fish around the tank; which was really cool. He also would sit on top of the power heads and stick a tenacle or two out of the opening waiting for us to give him a fish. I don't think he'd be a problem with the fish as long as the fish is bigger than he is and he's well fed. IMO
