So I'm going to try and make one of those simple yeast/sugar CO2 reactors I've read about, but I'm confused as to where I can get a check valve? aquarium store or lowes maybe? what size should it be. My airline tubing looks to be one of the smaller sizes. Also if I run the line into my hob filter intake, that wouldn't work because of outgassing as soon as it gets into the tank right? How else could I run the line without buying a diffuser. Trying to do this really cheaply to start out. Thanks for any help.