Smartest seems to be cichlids, though I have to doubt my oscar's sanity. I've been working on these 150 gallon growout tubs in my fishroom, one of them leaked a little last week. No big deal, as I got several used, the leaker is an outdoor tub. I started filling another yesterday, fill 1/3 & wait. It was holding fine, no leaks, so I fill it 2/3, & wait.
This is when the oscar decides it's time to rip off the spraybar & shove it partially out of the tank. I go down there, and have a small creek across the floor, looks like a slightly leaking tub. Looking around the tub for where it's leaking I see that it's bone dry. I start checking other tanks, hoses, etc, no leaks. I'm starting to think some of the house plumbing is leaking, and start following the leak back, looking up. This is when I notice the loose spraybar with water dripping down the back. I swear, this oscar had a smirk on its face, it just sat there looking at me. I was tempted to drop the heater down & let him drain his tank down to 1/4 full.