I have the same size tank. I can't use MP10s (acrylic os too thick), but even if I could, I worry that they would have to be turned down low to prevent a sand storm. If you are going to use them, it will have to be 2 at low speed, unless you are going BB.
My tank will be glass, so it'll be just the right thickness for either.
Honestly, that's a tough sand choice for such a shallow tank. I'd skip the MP10s and try more, less pwerful powerheads. I have some Tunze 6015s, which are pretty good because you can angle the flow up, but I think they'll move your sand.
EDIT: Add a tank link, so I can follow along.
Having four+ powerheads with wires running everywhere was driving me nuts, as the tank will be rimless.http://www.nano-reef...howtopic=298921
I really like the two mp10's idea, never had a 40, what about two 20's?
They don't sell MP20 anymore, but if you can find a place that has them, let me know, what I have seen is that they are less than MP10s used.
I'd still go with the MP10's...Adding a bunch of pumps to your tank is an eye sore You may get a little sand movement at first but things should settle eventually. Dial them down to a point that lessens the sandstorms and put them 2" from the water's surface. A good speed would be just under the speed that causes air to get sucked into the pump.
I can probably add a small piece of plastic to the top of the PH to keep it from sucking air down into it.
Yeah, definitely don't have that kind of budget. lol
Unless, of course, you're willing to donate to the cause!