Erratic herbie's?

[banditpowdercoat]

My Coast to coast overflow is really erratic on my 150g. One day its high, coming out the emerg drain. so I open the gate valve. Sometimes it takes a little bit to get the level down, other times, I have to open the valve alot. Then i'ts good for a while, then draining to much. Like a never ending battle on the overflow level. Nothing is getting stuck in the drain.

Anyone else have issues like this? it's making me mad. I do have the return pump(Little giant MQDX 4) feeding my skimmer and a Phos reactor as well. But those should be constant flow too??