I don't separate the wet and dry side of my viv with a divider like some do, I just pile up the gravel till it's above the waterline where I want dry. That allows the roots of the plants to get down to the water and help maintain it. As well, I feel the gravel provides a good place for the nitrobacter and nitrosomas to flourish and add their help to keep the water clean.

When I go to a larger viv, I do plan to have a circulation pump as I feel there'd be a benefit from added oxygen to the water from a waterfall or just a water cascading over some gravel in a mock stream bed. My plan is to keep the pump outside the tank though in another reservoir below the viv.