I just started a 90 gallon setup that I got from a friend. With it is an Eshopps RS-100 sump and he had an Aqueon Quietflow Submersible Pump. The siphon is working well and the water is flowing through the sump. The return pump seems to work too well. I cannot get the water level to remain at the "Water Level" line on the sump. It is well below the line and basically drains as much as it can. I have tried reducing the flow rate on the pump with no success. Does anyone have any advice? Do I need a new pump? Am I missing something very simple? When I initially started up the tank it ran for a number of days with the line slightly below the marked line. Now it drains all the way down in a few minutes. If you need any additional info on the setup please let me know.