Hello, here goes...

I currently have a very simple setup where the tank drains to the sump and a return pump pumps water back up. I have set it up so if a power failure occurs...there is enough space in the sump to accept the extra water that will drain.

Now...i'm setting up a separate refuge. So if you can picture this..the drain from the tank will be split and some water will flow into a different smaller tank and that tank will have a small pump pumping water back to the tank...how do i design this so its flood proof as i did with my current setup?

hope this is making sense.
thanks

This is not a good idea, IMO. If you are going to have a split sump and fuge, you shouldn't be relying on separate pumps to get things done. The best option, again IMO, would be to have the fuge situated higher than (or IN) the sump, and let gravity feed water from the fuge to the sump, and have one return pump in the sump returning your water. The way you have it, if one or the other of the return pumps fails, you're going to flood. With the gravity feed, if your return pump fails, you still have enough room in your sump to accomodate the water. There are other ways to acomplish the same thing, but this is the easiest IMO.

that's a great idea...i dont have room IN the sump...but i can see if i can fit a shallow fuge on a DIY shelf under the stand...great idea - thanks!