Fluctuating sump level

[reefmanta]

Please help….I am fairly new to the hobby and have a TMC 600 signature. Live stock happy and healthy but my drain to my sump keeps changing flow and I do nothing to it….the sump level keeps going up and down and it’s driving me mad!! What am I doing wrong. Photos attached of set up. Any help gratefully appreciated.

 

[rayadog]

Your return pump is behind the skimmer? Is that chaeto in front of the sock? Are there any … adjustable partitions?

 

[UncommonSense]

Oh! This tank’s drain plumbing definitely shouldn’t have any valves on it to restrict flow!

That could be part of your issue… more importantly, though, valving down a single drain to reduce noise (tuning a full siphon) can cause your display to overflow onto the floor if the valve ever gets clogged by a snail/etc!

Assuming your return pump is controllable, turn down return flow a bit and see if this helps, after getting that drain gate valve wide open! (Ideally omit the valves on the drain altogether; they are a water damage risk on a overflow design with no emergency drain!)