This is a more in-depth explanation of how to add CO2 into planted aquariums.
For more information on aquatic plant keeping, please read PLANT FAQs
What is CO2?
Co2 is Carbon Dioxide.
Why is it important?
Plants require CO2 to photosynthesize. Having more CO2 available allows plants to photosynthesize better and faster. In aquatic plants, this means the plants can grow faster, gain better coloration, and outcompete algae!
Some aquatic plants require added CO2, although almost all plants will benefit.
Ways to add CO2:
1. Compressed CO2 gas: CO2 gas diffused into the aquarium or through the canister filter outlet with a micro bubble diffuser. This system is the most stable and effective way to add CO2 into the aquarium. Over time, it can also become the most cost effective. For the initial setup you'll need: a cylinder of CO2 gas, a regulator with a solenoid valve, CO2 tubing, a check valve, a bubble counter, and a diffuser. You can purchase parts individually or buy as a kit! (Product links at bottoms of page)
2. Liquid Carbon: Bioavailable Carbon in liquid form. Many brands have some version of a liquid CO2. Easy dosing! Usually works better in smaller tanks with daily dosing. Caution: easily overdosed! Start with small amounts!
3. Tablets: Slow dissolving tablets. These tablets need to be replaced about every 3 days. Easy dosing but may cause fluctuations in CO2 and pH. Caution: easily overdosed! Start with one tablet and monitor pH. Remove if necessary.
4. DIY & Yeast Systems: Natural CO2 gas produced by yeast fermentation. You can purchase as a kit or DIY with minimal cost. Works best on smaller tanks, but no regulation of CO2 amount. Caution: no regulation means potential for large swings in amount of CO2 added. Can be overdosed easily!
How can you monitor CO2?
The easiest way you measure CO2 levels is to measure pH. As you add CO2 into the aquarium, the water becomes more acidic and pH will lower. A pH checker can be added to monitor pH to ensure you're adding enough CO2, but not too much!
The most cost effective and accurate monitor is a CO2 drop checker. This visual indicator can quickly give you feedback on the pH of your tank. A glass bulb is filled halfway with a solution that changes color based on pH. The bulb is inverted and placed underwater, so a bubble is trapped and allows for gas exchange.
Another option is Seachem's pH alert. This is a small plastic card that is placed inside the tank to constantly monitor pH. It lasts up to 6 months and is surprisingly accurate.
There are other options: digital sensors which can get quite pricey, and single use test strips which are not very accurate.
Is CO2 safe to use?
Yes, CO2 is safe to use. CO2 is nonflammable and noncombustible (It cannot catch fire or explode). However, is possible to add too much into your aquariums.
What happens when you add too much?
It is possible to CO2 poison your fish and invert! As mentioned, the water becomes more acidic when adding CO2. Some fish and inverts cannot tolerate very acidic water, and/or they can suffocate as the oxygen levels drop.
This is why it is recommended to use diffused CO2 with a regulator and solenoid valve. This is a more controlled way to add CO2.
It is also recommended to use a CO2 drop checker or other pH monitor. This allows for better control and less risk of poisoning your animals.
For any additional questions or advice, please email us or reach out on Instagram! We are happy to help!
List of recommended products:
Seachem Flourish Excel liquid CO2