contrary opinion
The Plant Gro system is quite well designed and but for the refill cost, is quite affordable. In a small tank where looks count, I doubt there is a better solution.
The response in any particular tank is dependant on the water, as is true for any CO2 injection system. The max tank size currently is 20 to 30 gallons.
The ramp type diffuser acts as a bubble counter since you can watch each bubble roll along. The prepared mix seems to be "snot" free and since there is no airstone, there is no risk of pressuring up and bursting the generator. The bottle is small and hangs on the tank so there is no risk of syphoning tank water into the generator.
If you don't have access to a power drill to prepare your own 2 litter bottle, or the tank is in a place where the generator and tubing and bubble counter would be unsightly, it is not a bad deal.
If you have a large tank, it won't be enough, unless perhaps your water is of low KH, but low Kh is always a concern, even with this CO2 method.
If you want high levels of CO2 it may not produce enough.
I have 2 of these systems running on 10 G and 20 G tanks, with supplimental DIY on the 20, mostly to allow me to experiment with gelatine mixes. (At the moment, that DIY seems to be leaking with no bubbles that appear in the bubble counter making it into the tank and the solid gelatine + ale yeast + baking soda + yeast nutrient is hardly producing at all, thank God I have the Plant Gro going with a DIY mix to keep the tank stable!) In my 29 G I have DIY CO2 with a DIY power reactor.
My experience is that the Plant Gro diffuser does not work well with larger DIY generators as it will not handle large or double bubbles and the gas is wasted.
