I think so.
I use to think food had something to do with it but... Nah.
I think it's tank mates. Big rays, and/or other big fish.. Usually from the armatus hitting something... iMO
I doubt food anymore. I feed both Tilapia and whole smelt. Alternating between the two.
As for as tankmates, they can definitely cause tank impact but I have not seen this one bash the sides like my other one who comitted suicide with the lid. Rays never go after him anymore. He just paroles the tank these days.....
Yes they beat me to it, being king of the castle definitely makes armatus feel happy and secure. I believe it's the same case with most monster fish. Exceptions being arowanas and doradoes who don't really give a **** and will think they are king anyway.
my rays really never bothered my last armatus. He was way bigger than the rays anyway. but all it takes is that one time the armatus gets spooked by another tankmate or even a tank cleaning. Its the only explainable thing i believe could be the cause of death to these beast.