I have a sump/fuge below my tank fed by an e-shopps overflow and returned by a mag5. I have had the overflow set so that the tank height is around 1'' from the rim of the top of the tank. I looked at it this morning, and it's almost overflowing over the top of the display. I haven't added water to the return section since yesterday morning. The overflow box is clean and the lines don't seem clogged with anything. I haven't touched the overflow in weeks. Why would this be happening? I've turned the system on and off a few times now this morning, and re-cleaned the overflow and its pieces, but the display tank returns to near-overflowing after about 20 minutes. I'm confused.