I've been going through old threads looking at aeration methods and I've got an aquarium pump and air stone, but I need an inline air filter. I keep seeing references to these, but I'm not sure where to get it. Can I buy it at a pet store near the aquarium pumps or at a hardware store? Also, if it's the hardware store, what section would it be in? I'm just not sure what it's used for outside of brewing and aquariums, so I don't have much of an idea of where to find it. Thanks for the advice!