If the pump delivers at the bottom at the tank, there properly wont be any waves at the top, but your idea will improve the design.

Regarding sideways movement, I was not talking about the gears, but the hose.
I like to explain out from my own experiments. I had a Ø8mm hose, 1,6mm wallthickness (3,2mm total). I used spring loaded bearings that pushed with 10Kg on the hose. I had a washer on each side of the bearing, so that the hose should not be able to move away from the bearing. In 2 of my experiments the hose managed to move past the washer, in only 1,5mm space. This of cause broke the hose.

It is very simple to adjust for that in the design.
It would be best to have a part between each roller, to align the hose in the center.
The easiest would be to have 6 planet gears, 3 acting as rollers and 3 between that dont push the hose but only aligns it.