Creating flow

[Parker]

If you have a cylindrical tank, how about placing a powerhead down in the rock work with a vertical spraybar? You would need to deal with the cord somehow.. If your rock work went to the surface you could hide the cord and the spraybar that way. Depending on the size of the tank you might be able to put something bigger in there, a Mag or some other submersible pump.

You may be able to run it the opposite direction..power at the top of the tank..spraybar facing down.. Need to hide the whole thing in the rocks though, if possible.