My lap does this. I hate it cause he scares the big endli and odoe and they start acting up a little too but then they realize nothings wrong and stop while he continues going crazy swimming up and down hitting the lid and splashing everything around the tank. I fear he will knock his self out some day. And he does it from the slightest thing I can drop something and it'll send him flying or it may not. He's bipolar.Sorry for your loss My del goes nuts whenever any of the fish spook it and rams into the aquarium. One day it slammed itself into the side of the glass so hard I thought his spine was damaged.
He was fine yesterday before and after wc. I sat there and watched them for about a hour after the wc like normal and everyone was fine. Only fish I was worried about was my lap cause as you read above he's crazy. The del wasn't an easily spooked fish I could pet it gently during wc or when it would come to the top to feed if I wanted.Sorry for your loss. Sometimes when a poly is about to go or experiencing unknown issues. I've also discovered that they will struggle swimming around and bang against the top lid.
Only light they get is moonlight through the shades at night. I doubt this is the case as polys and most of my fish for that matter are nocturnal IIRC.Awe man that sucks.. Out of curiosity, is the room completely dark at night? I actually keep night-lights at outlets near all my tanks to reduce the chances of freak-outs.
On another note I've been toying with the idea of rehoming all of my polys. Maybe it's time.