While all Tunze controllable powerheads are capable of being ramped up and down, gradually or quickly, the 7096 is designed to switch back and forth between the two set power levels. It's designed this way because it is a much more effective and natural way to generate random flow. That might be a little counterintuitive, so let me explain...
It's more effective because the best way to generate random currents and eddies is to have a high velocity stream of water crash into a slower moving stream. In the example you give, it would be the 70% power stream catching up to and colliding with the 30% stream. This collision creates more (random) turbulence than if the stream were gradually ramped up.
It's also a more natural way to create random flow. If you think about in the ocean, there aren't really any situations where streams of water gradually increase velocity. What you find in nature, especially around reefs, are higher velocity waves colliding with slower velocity (receding) waves.
But if you have your heart set on the gradual ramp up, there are 3rd party controllers that can do this with our pumps.
