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 in