drilling and over flow boxes

[The Grizz]

That sounds like a good plan, as for return pumps the submersible pumps are good and are reasonably priced. It depends on how much flow you want in the tank from your return. they do have there down side though, some pump can create alot of heat and depending on if you are going to run any media reactors with smaller submersible pumps they might raise the temp in your tank. Just for an example I have a total of 6 pumps running my 165 gal, 3 of each internal and external and my heater has never been on in almost 2 yrs, I actually have to run a chiller.