Hey guys so I've added a 10 gallon sump to my 29 gallon FOWLR system. I'm having a hard time matching the overflow rate with the return pump. I feel like every time I look at the return water level, it slowly gets lower and lower. I thought about evaporation but it gets so low that I don't think that that's the only cause for this. For the overflow box, I have the Eshopps PF- nano which is rated for 200gph (with 3/4in hard pvc) I believe and my return pump is rated for 320gph max (with 3/4in tubing). On the overflow side, I've added a valve so I can turn off the flow if needed. I've read that that should not be necessary but if I don't, the overflow makes so much noise and no water ever stays in the box itself before going down the pipe. And even with the pump at the max, I see the water level continue to rise. Granted I didn't leave it that way for long. Should I keep everything at the max/open all the way and just see what happens? Do I need a stronger return pump? Any advice would be great!!