Gas filters

Not only water is filtered in an aquarium. Sometimes it is also necessary to filter air, e.g. to remove carbon dioxide or humidity.

To increase the effectiveness of ozone generators, the supply air can be dehumidified.
If the carbon dioxide is removed from the supply air of skimmers, the pH value in the aquarium water increases slightly.
In rooms heavily polluted with tobacco smoke, essential oils (e.g. aromatic candles), diluents, the supply air of a skimmer should be directed over activated carbon to bind this substance. The activated carbon should be replaced monthly. 
Reverse osmosis plants, which are operated with very hard water, have a lot of carbonic acid in the pure water. This considerably limits the capacity of a downstream ultrapure water filter. A gassing stage removes too much CO₂ from the water.

Spare parts can be found at the respective size under "spare parts".