I think that that is going to create some serious dead spots, with the area immediately next to it been quite rich in CO2. Reason I say this as it looks to me like the only water current leaving the reactor is doing so straight down into the substrate.
An improvement would be to put a ceramic diffuser on the end of the line inside the bottle and to create some horizontal flow through and out of the bottle.
As it stands it's doing the complete opposite to what we all know as good, as in it's doing nothing to circulate, or allow the circulation, of the CO2 throughout the aquarium.
Back when I was doing DIY, I built something very similar to this. Ade is dead right.. alot of dead spots and also alot of wasted gas. I had far better results using an inverted jam-jar, with a flow passing across the opening, was much more stable as well.