I'm setting up a tank that is drilled in both back corners with a sump and thinking of using two return pumps. I'm trying to achieve good circulation. Anybody doing that? Any problems I'm not thinking of? I'd appreciate any advice. Thanks.
I would caution against plumbing two pumps together as they could work against each other. You want the pumps to pump as efficiently as possible and even identical pumps wont pump exactly the same flow. There would be nothing wrong with plumbing both pumps as returns keeping them separate as long as the overflow can handle the combined flow of the two return pumps.
You could also split the return line using a "Y" and only one pump but making it a higher flow/pressure pump. The nice thing about running two pumps is if one should fail, you have a backup.
just my 2