Your overflow location and your return/returns depend on the size of tank. I have a 150 cube so I have mine in the corner (it is drilled in the bottom corner) 2 holes only one return, one drain. If you are looking at a long tank you may want to do 2 returns and one or 2 drains. Some folks who don't want a bunch of power heads in the tank like to drill the back in a couple places and have a powerful external pump split the work thats called "closed loop" (search it tons of info im sure) Otherwise what I like is a slower flowing sump. I only have a quite one 1400 as my return and so my drain water (splits into 2 chambers refugium, and skimmer) and chills in the sump for a bit longer, giving it time to skim more and chill in my fuge growing my cheato. I rock a super reef octopus 3000 (LOVE it.) with the bubble blaster pump, and I have a lot of pooping fish and keep SPS so I can vouch for how awesome this skimmer works. I love starting tanks with the MB7 (nitrifying bacteria stuff from brightwell) Of another little thing I would never be with out is silly but it is one of those ammonia instant alert things you hang in your sump and keep for 3 months. I think that would be a big deal for fish only tanks cause you can let them get dirtier to a point but want to be in the know right away if you get a little ammonia spike. I feel like I am rambling but didn't really know where to start make sure you draw and plan out your sump how you want it... perfectly... plan your plumbing at the same time. There are formulas out there that help you determine what size overflow box and holes to drill... how deep to make your sump... set your baffles etc. You are doing the best thing asking questions and reading a ton. Hope we can help!!

Heidi