I used to have a 14" Trimac in a 4' 120 gal...
For a while there was a $100 bill under a rock at the bottom. I'd tell my friends, "if you can get it you can have it." When you reached for the lid to open he'd be right at the rim ready to attack whatever came in.
In all fairness, he bit be a couple of times. It would bleed but was essentially like paper cuts.
But he was frightening enough no one ever got the $100.