If he is eating well, and you have quite a bit of flow/current in there it could be that. I will say his spotting at the
perimeter seems to be running a little.
my male once in a while looks almost like he is sneezing. it's not often, and he'll only do it once, but all of his disc will curl upwards like a person getting rdy to sneeze, and then ACHOO it all goes back down again. i've only seen it twice since i've had him, but it looks scary and i run over to make sure he's not deathcurling.