What You Need to Know about CO2 for Planted Aquariums

Just like grass and trees, aquatic plants also require carbon dioxide (CO2) to photosynthesize. CO2 is a gas in its purest form but like oxygen, it dissolves in water. This dissolved CO2 is essential for the growth of aquarium plants.  Managing CO2 in your planted aquarium is a tricky business. Too little of it will hold back the growth of your plants, while too much of it will be harmful to your fish. Therefore, it is important to maintain a healthy regulation of CO2.  To maintain an optimal level of CO2 in your tank, you may require a CO2 regulator and a CO2 diffuser along with a cylinder. There are a number of ways in which you can safely introduce additional CO2 in your planted aquarium to boost the growth of your plants. Let’s have a look at a few of them.

Pressurized CO2

Bottled pressurized CO2 is readily available in the market. Bottles having electronic solenoid valves allow you to easily introduce CO2 into your tank. The solenoid valve will allow the CO2 to enter the aquarium only during the day because plants do not photosynthesize at night.  This will also prevent unwanted changes in the pH levels of your tank, which can be caused by an excess of CO2.  Although pressurized CO2 is the easiest and most reliable option, it is also expensive. You will have to refill the bottles regularly and it may take some time to figure out the optimal CO2 bubble output for your tank.

Liquid CO2

Liquid CO2 is an option for small aquariums but it is not really CO2. It is simply a liquid formulation of carbon. Clearly, it is not the best substitution of CO2 for your plants and eventually becomes cost ineffective. Moreover, liquid CO2 need constant addition and adjustment in the tank. Despite the drawbacks, you can use liquid CO2 for small planted aquariums and lower-light tanks to fight algae.

Electronic CO2

CO2 can be produced electronically. A carbon rod is electrolyzed in the aquarium to produce CO2. It allows you to set a timer for releasing C02 in the aquarium. It is advisable to utilize this method of producing CO2 only in small tanks because higher levels of CO2 production can get expensive. Moreover, refills cost a lot because they are specialized for each machine.


Generating CO2 yourself is the most cost-effective method. You can easily set up a DIY CO2 system by using cheap materials that are readily available in the market. It is easy to set up and inexpensive to refill.  The only drawback of a DIY CO2 system is that it causes a layer of slime on a standard diffuser. You can easily tackle this problem by injecting the CO2 directly into the filter. Sometimes, a DIY CO2 system can be hard to monitor because despite being easy on the pocket, it cannot be timed and will continue to run at night.

To sum it up, pressurized CO2 should be the first choice for a planted aquarium, if your budget allows it. Otherwise, a DIY CO2 system will work just fine. So go ahead and introduce CO2 in your planted aquarium to give your plants a healthy boost of growth!

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