My Modular Marine bean animal had been working fine. After the latest water change, the overflow was draining all the water out of the emergency drain. I pulled out the outside box plumbing, cleaned it, and that stopped the total drain. But now, the box won't stay full of water, it gurgles, and won't maintain the correct water level in my sump. Checked the gate valve and it is fine. This is happening with the gate valve closed some. The second drain has always had a lot of water coming out. Is that normal? Should I have that second drain cut shorter? Any advice?