Custom Mangrove Sump....pump

Hey all I am thinking about setting up a mangrove/cheato sump for my new 40B. I will get the tank drilled if I do decide to implement it.

It is a custom design with one large seterilite/rubbermade plastic container 36gallon. It contains two smaller containers, one for the line from the tank to empty to and overflow into the rest of the sump, the second container will hold the pump and water will flow into it through drilled holes.

I want to fill the whole thing with sand and have the other containers sitting on top the sand. I will plant mangroves througout and also throw in some cheato.

I want the container to stay at about half full so the mangroves can grow out the water and to leave room for overflow in case of power outage,

What type of pump/flow would I need??

I have attached an extremely crude paint schematic lol

 

I would look for something that pushes around 600gph.