I have used them for almost a year now. I had two running on a 20 gallon planted tank, and rarely had enough CO2.....even with a power reactor instead of the passive reactor it comes with! I think it is a real nice, discrete-looking, low-to-moderate light tank CO2 system. It doesn NOT work well for high light tanks.
If I was to use this system again, it would be on a tank that would grow fine without added CO2 being necessary. Then when you do add it, plants will grow even more lush and beautifully. I would not use it on a tank that REQUIRES CO2, though! I have fought algae for a year now, and have recently (just last week) upgraded to a 55 gallon with Pressurized CO2. WHEWW! What a releaf!
