Last year I built a regulator and have been injecting CO2 for many months now. At first I saw no improvement in my plant growth or algae control, but I was just bubbling the CO2 into the return pump of my sump. I decided that it was probably not a very efficient way to get the CO2 into the water so I built a Tom Barr style CO2 reactor with Venturi loop. And yet I still see no evidence that adding the CO2 has made any difference. Well, the one difference is that the CO2 reactor gurgles loudly all the time, but other than the noise pollution I've noticed no benefit. I decided to further investigate by getting a decent pH tester because I really couldn't see any measurable change on the test strips. So with the tester I now know my pH starts at 8.2 and goes down to 7.2 with the CO2 turned on. I would describe my CO2 injection rate as "too many bubbles to count." I have a 30 gallon tank which is drilled and has a small overflow box, a Herbie style drain into a 10 gallon sump with trickle filter. The trickle filter is duct taped to minimize CO2 loss. The reactor has it's own pump that sits in the sump. It sends CO2 enriched water directly to the intake of the return pump. I have only one fish, a bristle nose pleco that shows no sign of stress. I have a crypt, dwarf sag, and a couple other plants I can't remember the names. They look like crap and algae runs rampant. My substrate is aquasoil Amazonia. I haven't been fertilizing. The plants look to me like they are CO2 starved. I'm at a loss.