Aeration system, without the air pump. Most aquarium style air pump will work, we recommend a deep water pump. Comes with inline filter, stainless steel diffusion stone, and tubing. About the inline filters: There are two sides to the filter – an “in” and an “out”. The direction you use doesn’t matter, however, you want to take note of which way you first push air through it and always keep it that way. There is an arrow on the edge of the filter housing that we use to keep the air flow going one direction when using it. The filter should never get wet, so don’t try and sanitize it by dunking it in sanitizer. To store the filter, use a little tinfoil on the “In” of the filter and store in a zip-lock bag.