Herbie drain - Fluctuating overflow level

[Potatohead]

I'm hoping it will settle in time. When I make the adjustments I am turning the valve the smallest amount I can feel, like maybe a 2° turn. I'm hoping it's stuff building up in the pipes and it will settle down.

I designed my system so that even if I lost all draining from the display, the return chamber is sized and the ATO is on a time limit so that it will never be able to pump enough water to flood the display tank. That will likely kill the return pump but that's not a huge deal... So I am not too concerned about running a trickle if I have to (I have tried it) but if the trickle becomes a little larger trickle it starts to make noise.

At the end of the day I'm not all that concerned with it because if the level falls a bit, it's still quiet which is the main thing for me. My only real concern is that let's say the ATO fills the return chamber to the max level, then the level in the overflow falls over the next couple hours, this raises the level in the return chamber even more and it sometimes triggers the high level alarm on the ATO, which is annoying. Or, the opposite happens and the swings on salinity are greater than they should be (albeit still small).