The Milwaukee regulator assembly can be used very well for CO2 injection in an aquarium. But, you have to be aware of its weaknesses. You have to always make sure the regulator is set for zero pressure before turning on the CO2 at the bottle valve. You have to expect leaks at the bubble counter, and either repair them some way or remove the bubble counter. You have to expect the solenoid to have a limited service life. You have to be willing to fiddle with the insensitive needle valve. But, you can do all of that, and then it works fine, and the price tends to be right.