I got a few small hatchet fish and I noticed one seperated and sort of having trouble staying towards the top of the tank and occasionally floating almost on its side.

I moved it to a small hanging netted box with minimal current and after a few hours they seemed to settle down and this morning they seem able to stay upright hanging out at the top.

I'm guessing the poor thing just ended up in a more turbulent area (they were right near an air stone going at full speed) and tired themself out fighting the water.

Sound like a likely explanation? I'm leaving them seperated in the netted box for a while longer just to keep an eye on them but I'm hopeful it's not anything more serious.