return pump and sump issues

[jadeguppy]

I am almost done with my stand for a 40g (reg.). Since it will be 3 1/2 feet tall for viewing when standing, I have plenty of room inside. I plan to ues the 3 15g cubes that I have for the sump system. One has a center hole that will feed to the second one below it (it will be on a small stand). Then the other will have a pipe attaching the drilled holes on each tanks side or I might raise the second tank a little to create a faster gravity feed. What type/ brand pump should I use for a return. Is an internal pump better or an external pump? I am considering splitting the return line and installing educators. The return distance is approximatly 4'. If things work out right, I may even have room for a small shelf area to house other stuff. Any ideas or suggestions on the sump design is also appreciated.

[poppin_fresh]

Eductors require a pump that can move a lot of water under pressure. I think you will run into problems because you will have to move a large amount of water through the sump to make them work properly. The side effect will most likely be poor filtration and micro bubbles.

As far as whats better, external or internal, its more a matter of preference. Internal is usually easier to plumb, but can add heat to the tank. Externals always run the risk of leaking, but they wont add as much heat.