How Does CO2 Affect the Water in an Aquarium?

Carbon dioxide (CO2) is a gaseous compound with soluble properties. It’s present in all aquatic habitats, and it’s generated by fish through an exchange process involving their gills. You may have heard about CO2 being toxic in high concentrations, but this isn’t really the case. The problem with high CO2 levels in the air or aquarium water is that it causes suffocation because of displacement of oxygen molecules. CO2 must be balanced in any habitat. In the specific case of freshwater planted aquariums, a deficiency of this compound will complicate things for certain species.

CO2 Generation in Aquarium Water

When water is added to aquariums, it normally contains CO2 that’s eliminated the moment it’s agitated and comes into contact with air. This creates a natural gaseous exchange. Bubbles generated by aeration pumps and air stones will release dissolved CO2, but higher concentrations are generally achieved through the fish respiration process. For the most part, fish keepers who properly establish their tanks through the nitrogen cycle usually don’t have to worry too much about CO2 levels. However, aquascaping enthusiasts have good reasons to generate higher CO2 levels.

CO2 in Planted Tanks

Most of the aquatic plants included in aquarium starter kits are able to grow in low-light conditions. For example, freshwater Java moss, Java ferns, and hornwort don’t require special lighting to grow and thrive in the tank. Moreover, these species aren’t the kind that need extra CO2 to maximize their growing power. When you get into the art of planting lush aquatic gardens, an activity known as aquascaping, higher CO2 generation is needed because of its nutritional properties.

CO2 and Water Acidity

Aquarium water doesn’t have to be pH neutral. Low pH levels increase acidity while higher levels result in alkalinity. The ideal pH for most tropical fish is slightly acidic, and this can be promoted through higher CO2 levels because this gas dissolves into carbonic acid molecules that are released into the water. Fish are more receptive to acidic conditions than they are to higher alkaline levels. When the pH level of aquarium water in a planted tank hovers around 6.6 and 6.4, there will be a benefit to fish scales, and some species will display more vibrant colors.

The Right CO2 Balance for Planted Tanks

For most tanks stocked with both plants and fish, the ideal CO2 concentration should be 30 parts per million. If the pH level drops below 6.6, the CO2 levels could be higher than 40 PPM, but this is still a safe concentration for most species. Exotic aquatic plants tend to be more delicate, which means they’ll need higher CO2 concentrations and brighter illumination. To this effect, you should add fertilizer that promotes CO2 generation or install a CO2 injector tank, but you’ll have to keep an eye on the pH level so it doesn’t fall below 6.4 unless plants are the only species in the tank.

If you have additional questions about maintaining the CO2 levels in your planted aquarium, reach out to the aquarium experts at Aquatic Warehouse. We are a leading provider of supplies for freshwater and saltwater aquariums as well as koi pond supplies. We’re located in Kearny Mesa, or you can order everything you need from our website and have it shipped to you. Call us today at 858-467-9297 with any questions you have.