First post here, though I've been on other forums for a while. I will soon be setting up a 240g heavily planted tank, my dream tank. My current plan is to have a sump, probably my 75g tank, with two return pumps (quiet one 4000's). I have heard a few things about the venturi like the Mazzi's and wonder if it would work with my setup. It seems from my reading that sometimes these are difficult to pick and work right, and I dont want to be spending lots on something that wont work, already kinda over budget. The other option it seems that folks use with sumps is to simply bubble co2 into the intake side of the return pumps... will this suffice?

And wondering, due to the size of the tank will there also be any special needs to keep o2 levels up? Will simple agitation at night in the sump via airstone/powerhead be enough?

Thanks for any advice, want to make sure I got a solid plan before I start buying to much stuff...