There are some awesome Rubbermaid sumps out there. Used to be a build by "spinner" if I remeber the user name right on Reef Central that did a cool one with a 300 gallon tub. The only downside I saw when I had one was the irregular shape makes baffles very difficult but if you don't do it the ATO is a little of a challenge. Also no sweet place to hang stuff with the supplied brackets that come with most reactors, probes, etc. If you have the space plumb them both in and use the Rubbermaid for a fuge!