means it doesn't like your 1) flow 2) your lights, or 3) combo of both.
My bta has decided to move after 6 months in the same spot. I know why, i cleaned out my pumps saturday and i think i put the nozzle at the wrong direction. so try to figure out what it doesnt like and try to fix it.
can create sort of a cave like area to prevent too much flow, but if it's looking for better lights you, and it, are in trouble.