Hey all- I've got everything assembled to make a small DIY filter for my small first time grow except for the carbon. I've read in a few places that we want to be using carbon specifically for air (as opposed to water/fluids). But everyone suggests getting the carbon from the pet store, which is for aquarium tanks (presumably for water). Does anyone have an explanation for this or guidance on which carbon to get? Essentially, I just want to make sure I buy the right carbon for our use. Thanks!