One reccomendation, no need to drill into the housing, a simple inline tee/barb setup on the inlet hose would have dragged the CO2 into the filter just as effectively. Some media in there to brak up the bubbles and you have a filter/CO2 reactor.
Very cool though Craig.
Unfortunately with the space restrictions and really short tubing I have there was no room. I'm really impressed with this setup as a reactor, flow is much less restricted and CO2 diffusion is just as good if not better then the PVC reactors I was using.
Why use two elbows on the filter head? You would get less head loss with straight fittings, with the hoses curved over a large radius. (Assuming you have enough room to do that.) This almost has to work very well. and it should keep the CO2 bubbles from escaping at a higher bubble rate than the usual DIY reactor does. If I used CO2 now I would definitely make one of these.
The 2 Elbows was a space issue. With everything plumbed through the bottom of the tank I have very short hoses and little room to work once I have everything Eheim 2217, CO2 Reactor, Inline heater plus the UV.