Down graded to a Hydro 525. Flow from the 1350 seemed too high for the fish in the 40 gal set up. I will program the timer to run the 525 for longer periods of time. I will probably start with 45 min on and 15 min off. The 1350 was set for 15 min on 30 off.
Found fish were getting sucked into power head ( hydro 1350) swapped to the diffuser head to displace current flow. If this doesn’t work will need to down grade the power head.
Added a air pump and stone to increase air circulation.
Lost 4 zebra danios. Not sure as to why.
Lost all but a few fish in Feb 2021. Power outage lasted 3 days. Used blankets and battery operated air stone at the time. Lowest temperature in tank was 57 deg at one point.