If the power goes out then the water drains into the sump from the fuge AND the display tank. To prevent an overflow, you simply need to make sure there is enough room in the sump to handle the extra load. What that means is you don't keep the sump full of water. If you look at the pic of my sump again you will see that it's not totally full. _________ 125 Gal Reef. Born March 2002 FISH: Ocellaris Clown, Yellow Tang, Fairy Wrasse, Sand Star, Fuzzy Dwarf Lion, Mandarin Dragonette, Hippo Tang CORALS: Green Striped/Red/Purple Mushrooms, Green Star Polyps, Yellow Toadstool Leather, Bubble, Frogspawn, 2 Hammers, Yellow Polyps, Open Brain, Ridge Leather, Various Zoas, Button Polyps, Kenya Tree, Colt, Elephant Ear Mushroom, Clove Polyps, Torch, Purple Clam, Rose BTA |