I bought a used 180 that's pre-drilled for a sump, no plumbing attached. I've been researching on the interwebs and most good articles come from this site, so I'll look here for help. My new tank has two corner overflow boxes, each with two holes. One is 1-inch, one is 1 3/4. I've figured out the first part, the drain, I think. The second part is what to do with the two returns. I've read some stuff that says two returns is overkill. So here's my question(s): Should I have two returns or one? If two, should I get a pump with dual output? The article against two returns argued that plumbing two returns from one pump reduced the efficiency. Thanks.