Hi all! I have a 110 gallon acrylic reef style aquarium. Top pretty much sealed with 2 22" x 22" cut outs. I have a lot of experience from 20 years ago with Cichlids and UGF's, but want to try canister filtration with Cichlids. My question is: I have an internal overflow box in one corner. It has one pre drilled outlet hole maybe 1 5/8's" in bottom and two one inch return holes 1 inch from top in the aquarium space. If I lose water to evaporation the canister filter will run dry right?. Can I gravity feed a 20 gallon underneath tank and have the canister draw from it? For returns I could use a "y" type splitter to return to top two holes? I would get cascade 1500 model I think. Thanks in advance for any advice. PS. I already have a 20 gallon and 55 gallon in storage.