Pushing a thousand litres of water

["Greger Lindstrand" <greglind at algonet_se>]

Some weeks back I was told that I needed to push at least 1000 Litres /hr thru my Dupla Reaktor S in order to ensure the CO2 is always at the correct level to maintain the Ph level steady.

I use a Ehiem 2252 which (at least when it was new 18 years ago) is able to push 1250 l/h of water.
With the CO2 system engaged  on the Reaktor S, the Eheim manages to keep 192 l/h output of CO2 enriched water.

Ok, I figured that it wasn't strong enough so I got myself an AquaClear 5000 powerhead to do the job. It's good for 3550 l/h and can lift 200 cm of H2O.
I was astonished when measuring the output of CO2 enriched water from the Reaktor S. It was exactly the same 192 l/h!!!

Dimensions of the hoses in and out of the Reaktor S, is 8 mm.
CO2 pressure is the same (no change on the settings).

In spite of the much more powerful pumphead, I have the same flow of water out of the CO2 reaktor.
Is there an explanation to this?
To me it is an hydrological mystery without any logic in it.
How DO you push a thousand litres thru the reaktor?

/Greger