Has anyone have any experience with under gravel Jets?
They keep debris off the subtrate by moving water out the jets and push all debris towards the filter. I'm thinking about making one for my 280 gallon tank. I'm just not to sure on the size of pump i should run.

Here is a couple links on it.

http://www.cichlid-forum.com/articles/ug_jets.php

This shows you a pic of the undergravel jets.
http://www.cichlid-forum.com/phpBB/viewtopic.php?t=190145&postdays=0&postorder=asc&&start=45

I see what your talking about now, like a close-loop on marine tanks.

Your could do it will your setup now and prob. be easy. If you wanted to do a close-loop system. Your drains will feed your pump and use your returns to feed the pipes you hide under the stand. If you did that you wouldn't need a sump nor have to work about water on the floor when the power goes out. But, you would have to get 2 FX5's or something for filtration or use overflows to seed your sump. Just idea's thou.
I guess one way check values would work when the power goes out as long as sand doesnt get in before they close. on a open system.