I am looking at making a DIY CO2 Absorber, and I am considering two different options.
The first is spin off of the traditional Rex Grigg or Cerges style reactors where CO2 is trying to rise against downward flowing water. The twist here is that I would make the body "conic" instead of cylindrical. Since water velocity is a function of flow rate and cross-sectional area, I can get CO2 bubbles to "hover" in the water column by expanding the the cross-section. (Hopefully) no air pockets to create noise at the top or bubbles blown out the bottom.
The main challenge with this design is narrowing the top down enough to make sure that bubbles cannot reach it and form a gas pocket.
An example of the "conic" reactor. Not really conic due to difficulty in construction, but will function nearly identically. Water in the top, out the bottom. CO2 will be introduced upstream of absorber and flow into it with the water.
The second is a more technically intricate design that tickles my inner engineer. The only mention I have seen of this design in aquaria is by Rezco, who has mentioned it here
. Essentially, we capitalize on the bubble that forms at the top of the reactor by spraying water onto packing with a large surface area (macroscopic, not ceramic pellets). Since absorption primarily occurs at boundaries between CO2 and water, this method will ensure highly effective CO2 absorption.
The issue I have is that the CO2 absorption is not readily controllable except by changing water flow-rate with an array of pumps or motor controller (both are pricey). Another issue may be algae or other bio-growth clogging the packing, I have seen this issue in person while working on similar equipment used to scrub chemicals from exhaust gas.
Ultimately, either design will probably be overkill for my 40B.
Has anyone made either of these before and wants to chime in with experiences or advice? I like to look before I leap.