Aside from the cost of your system, you may be wondering how much it's going to cost over time. This not only depends on the size of the system you are using as well as the amount of CO2 you’re using. In the home aquarium we aim for 30PPM of dissolved CO2 for happy plants and healthy fish. The amount of CO2 you use will depend mostly on aquarium volume and pressurized CO2 tank volume (most often referred to in weight 5, 10, 20LB bottles are common)
Generally there are two ways to add CO2 to your aquarium; either by disposable cartridge or refillable bottle.
A refillable bottle is the best option for long term cost management as indicated in the table below. We recommend a 5lb bottle for up to a 50 gallon aquarium. Above that, it is more economical to use a 20LB bottle, however a 5LB bottle is a lot easier to hide inside your stand than a 20lb bottle so take storage of the bottle into consideration as well. Notice that the Fluval numbers are based on WEEKS and the "up to X0 US Gal", it's per cartridge!
The fish keeping hobby is one of patience and an investment in an pressurized CO2 system is one that will keep your aquarium stock and plants healthy for years to come. It's important to remember that a CO2 system is not a treatment or a fix. To maintain the environment of your aquarium, CO2 will become an ongoing cost.
Want to know more about the relationship between bubbles per second and 30PPM of dissolved CO2? Click here.