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What size CO2 cylinder should I get for my planted aquarium?

If you are running a high tech planted aquarium injected with high amounts of CO2, people recommend getting the largest size possible so you will not have to refill the cylinder as frequently. However, for the average customer, we often suggest:

  • 2.5–5 lb. cylinder for 20-gallon aquariums or smaller
  • 5 lb. cylinder for 25- to 40-gallon aquariums
  • 10 lb. cylinder for 55-gallon aquariums or larger

If you plan on using one regulator with five or six aquariums, then scale the CO2 cylinder size accordingly.

For more information on CO2 systems in high tech planted tanks, read the full article.