Yuri glad to see you trying something new. Hope you have lots of pleasure setting it up and getting it working.
I am not quite sure i understand why you might not want the reactor with the pump. The pump only circulates the water within the reactor to fluidise the Rowilith C. (Rowalith C is a combination of calcium carbonate and a type of magnesium mix) The pump does not feed the flow of water through the reactor. That is best done with a peri pump.
But if you can explain why you do not want the pump i might be able to come up with an alternative for you.