CO2 aquarium reactor

I am having some fish tanks, and they are fertilized with CO2. The main problem with glass diffusors is, that a lot of co2 is lost bringing it into the aquarium. Bubbles move to the top and evaporate into the room.
So one of my tanks with 700ltr was consuming a 2kg bottle in no time.
The tanks are running with HMFs (Hamburger mat filters) and a simple pump behind.
I tried some glass diffusors under the pump, but the pump is noisy with "air" in it. So I thought about an inline reactor instead of a diffusor. Having started with a connector for the outlet tube, the concept evolved to a small tank, filled with Siporax.

The concept is simple and effective: Water is coming from the pump (300 l/hr) on top left, into the reactor. CO2 is coming in from the bottom, the CO2 tube is halfway or more to the top. This is preventing any leaking of gas on the top i have observed with some prototype. Water passes along, and CO2 is absorbed at a dramatic rate. You are hardly seeing some