Posted: Mon Nov 10, 2008 1:42 am
I think that joshr needs to read the other posts in the thread before posting.
To answer you question, moldygrape, I have two tanks plumbed to the filter, a 100 gallon and a 40 gallon. You're supposed to turn the water over 5 times an hour, so on the 100 gallon I have a quiet one 2200 and on the 40g I have an aquaclear 70. For an 80 gallon tank, you need a pump that's rated at 80*5=400gph. I know it seems like a lot, but believe me, high flow is what keeps it clean when there's turtles. Don't forget to buy a pump that can pump that much water at however much head you'll have. The 'head' is the vertical distance from the pump to the edge of the tank.
Note that if you're not technically inclined, I don't necessarily recommend this project. Building a sump can be tricky, because you have to plumb things such that the sump will not overflow. You don't want a lot of water on your floor! One thing that comes to mind to make this project easier is to elevate the sump tank above the display tank. That way if your pump turns off for whatever reason, the 80g tank can easily take on another 5g of water without overflowing.
-robind