I plan on having my Fluval 203 feed the refugium and then having a ViaAqua return the water to the tank. Is this OK? If I do gravity feed I am worrying about flooding the house if I lose power. < gravity feed much idea if one of your pumps would shut off it would either keep pumping water from the tank to the refugium or drain the refugium I have plumbed many tank and trust me drilling a hole and putting an intake screen over the bulkhead is a way better idea Use a big bulkhead and it will not overflow > better With my system if I lose power the both the Fluval and water pump shut off together and when power comes back on they should both re-fire. The refugium will be under the tank in the stand. I am going to try something weird. My refugium has three compartments. In the first one, I plan on the Fluval feeding a tiny 12X3X6 reverse flow undergravel system with Matrix and Eheim Lava rock and m