Disposable CO2 Refills. 3 x CO2 refills for Plant Growth System 60. Most aquarium plants do not thrive without CO2 fertilization. So without extra CO2, your new plants can suffer and algae will take over your tank. A simple and inexpensive way to supply extra CO2 to the plants in your aquarium.. Easy to install, use and maintain.. Suitable for starter-sets, where even small amounts of extra CO2 will make a positive difference for the plants.