thanks for all the input, what i went ahead and did was the siphon setup that i linked above. i must say, i'm very impressed. i tuned the siphon so that my refugium is just the right amount of flow, and it is whisper silent. i was amazed at how quiet it was. i tested the system by blocking off the main siphon drain, and the drain into the refugium picked up the slack and handled the flow without incident. i closed that drain, and the emergency durso kicked in and handled all the flow without incident. so unless all three drains are obstructed at once its failsafe. and even if all three were blocked at once it wouldn't flood, it would just run the pump dry (i would consider that the lesser of two evils). and the system starts up from being stopped without any trouble, takes it a second to purge the air, but then it works fine without any adjustments. theres also almost no bubbles in the sump or refugium and, again, unbelievably silent. the loudest thing about it now is the mag pump.