i had a red tailed black shark about a year and a half ago. i had to treat the fish and clean the tank so i put the fish in a different tank and cleaned the other one. the tank with the fish (new tank) had no lid so i put a tray on top but there was a hole for the airhose and filter wires....etc... i went upstairs and came back down, checked on the fish, no shark , looked around the tank, no shark, checked the dogs mouth, no shark, then i hears a sort of wet flapping noise and looked at my foot and saw him. he was 5-6" and he fitted through the hole. i didn't know how long he had been on the floor so i scooped him up with my hand and put him back. i learnt a lesson. always have a lid.