you'll be fine as long as your pump doesnt pump more water than your overflows can handle. if that's the case, just get a ball valve on the return line and you can cut back on the flow
So, for the fuge I was thinking of getting a 10 gallon long or leader. Instead of having two overflows, could I just have a small pump bring water from the sump into the fuge and then have a siphon bring the water back to the sump? I'm fairly certain my return pump can handle this load because my tank is nearly full while the sump is an inch from sucking air. I think I need to lower my overflow box into the water more?
Sorry for the horrible pic but, something like this. The black being the return pump, the purple being the smaller pump taking water from the sump to the fuge and the red is the siphon bringing water from the fuge to the sump. Would this work? Especially with the question of my overflow box in my last post?
IMO the least of your problems would be how do you start the syphon. Save yourself a lot of trouble if you want to go with two tanks drill them both and connect with PVC