Vigorous water movement is necessary for a healthy mixed reef — but the powerheads used in most tanks are an eyesore.  I wanted to design my tank with a well hidden closed-loop circulation system to provide the same benefits without the clutter.  Rather than implementing a single circulation pattern, however, I also wanted to have oscillating movement that could be automated and controlled.  The solution was to implement a controllable water distribution switch (the derKroon FlowWolf) and a controllable DC pump (a Waveline DC-15000) in a six-way closed-loop system. 

In addition to the circulation provided by the closed-loop system, the sump overflow and return system provides additional water movement.  Water skimmed from the surface of the display tank is drained from the overflow by a three drain line “Bean Animal” arrangement (a system of fully-submerged drain standpipes that prevent ‘gurgling’ noises associated with air in a drain line) to a sump tank. Rather than a single return pump (which would represent a single point of failure), dual controllable return pumps, alternately ramping up and down, return water from the sump to opposing sides of the tank to create a gentle oscillation on top of the vigorous water movement of the closed-loop system.