I've used the Carbo-Plus unit. It is simple to install and use but it is very expensive to operate compared to DIY yeast and pressurized tank systems. IMO and IME they are limited to about 40G tanks, larger tanks won't see enough CO2 dissolved. A couple other little annoyances, the process eats (consumes) carbonates so care must be taken to replace those regularly to avoid pH crashes. And the process produces hydrogen, under certain circumstances this could result in the formation of hydrogen sulfide and kill fish and/or plants...this would be rare, with a very tight fitting cover, etc. Anyway, if you want easy, and price isn't a factor, and the tank is less than 40G they're a pretty good system assuming the other cautions noted.