Peter,
You can set it to whatever speed max/min, and frequency. If I were building the one for Nelson, I would build it as a double duty install. At low speeds it would act as a closed loop, getting water from the current overflow comb and pushing it out the bottom. At high speed/low intervals it would create very efficient pulsing flow. This way you could have a gentle night mode, feeding mode, and wave mode. Nelson's tank is very stout, well built, and I believe capable of handling this flow, but many tanks are not. You have to be very careful about using this method in a tank that is not over-built.
There are multiple ways of controlling a wavebox pump from using knock-off type wave controllers, the Tunze controller, or even the Neptune AquaSurf, which is a wicked superset of control. These all ratchet up the cost though. I have a pretty clear vision for how to build Nelson's wave box, but again, adding a sump, and his particular install needing to be quiet complicate the proces. Waveboxes tend to be a bit noisy, so I can understand his hesitation.
We originally drilled a hole in the lower part of the overflow to act as a closed loop with a press-fit MJ mod, but what he found later is that the mod was pushing so much water, he couldn't keep his sand bed in one place. This would again be an issue if he decided to go ahead with the wave box.
Just some thoughts to share.