[hahnmeister]

This is why systems that have a 'night cycle' never made sense to me, except in one respect.

Some systems, like tunze stream controllers, hare a 'night cycle' which lowers the flow at night. This doesnt happen in the wild. The only reason for this is that in the wild, fish can scoot off to some other 'less turbulent' locations to sleep... something they cant do in a captive reef as easily. But on the flipside, the night is when corals feed, and deposit calcium (grow), so you dont want to restrict flow at this time.

My suggestion is to make sure your fish have designated hiding areas with lower flow in the tank, so they can get a good night rest... but keep the flow constant.