You can add to the bioavailable carbon/CO2 as noted above through a product called AAP/NilocG Enhance or Flourish Excel by AAP/Seachem. This is probably the most simple way, in my experience. Or, you may use a CO2 generator/system, which can vary greatly in cost and CO2 delivery.
While AAP Enhance & Flourish Excel is claimed to work carbon source for plants, I believe that AAP Enhance & Flourish Excel work more by limiting algae growth on plant leaves, allowing the uptake of carbon naturally produced in a healthy aquarium that would otherwise be used by the algae growing on these leaves
We specialize in CO2 regulators for the planted aquarium
For this reason, Wet/Dry, many HOB, and even many canister filters are not always the best choice for planted aquariums (especially for the "Walstad Method").
Wet/Dry, in particular, will strip CO2, as will many Hang-on-back (HOB) filters, and some canister filter set-ups (although a proper set of your canister filter products such as Matrix or Purigen along with LIMITED water spray in return can help).
CO2 Systems - Green Leaf Aquariums
Mean Harri, have a look at my photos, particularly the present flooded Amazon forest 90g aquarium. I consider this tank thickly planted, even more-so than my others. There is no CO2, light is less than one watt per gallon of full spectrum/cool white combo (one tube each), and twice weekly liquid fertilization. The fish load varies from 75 to 110, all characins, Corydoras, three Farlowella. Obviously there is a balance that works.
HOW TO: DIY CO2 for planted aquarium TUTORIAL - YouTube
learly one of the main factors that attracts people to planted aquariums is the apparent ease of maintenance and how easily plants can grow under a wide range of conditions without any help from the aquarist. This is absolutely true but it is not always guaranteed that plants will take to your particular system and it is mostly applicable to the weedy type of plants. The aquatic gardener who chooses to never dose CO2 or any kind of macro or micro nutrients will be shooting themselves in the foot and missing out on a big part of the freshwater plant hobby. Without dosing it is much more difficult to grow some of the more exotic water plants and plants that are more robust, more beautiful and more colorful than those that are left to scavenge for what limited nutrients may be produced in the aquarium.For growers of "air" plants, carbon dioxide as a nutrient is never an issue but in the aquatic environment, CO2 is almost always the most limiting nutrient to plant growth; without CO2 photosynthesis doesn't even get going and your plant growth will reflect the extent to which you are adding carbon dioxide. Like using a protein skimmer in a marine aquarium, dosing carbon dioxide for aquatic plants one of the few keystone husbandry practices: with adequate CO2 your plants will grow better, faster, and they will be better able to outcompete undesirable algaes that can take over and cause so many people to walk away from aquatic gardening. Also, like a coral's relationship between lighting intensity and water flow speed, the more light you give a water plant the more CO2 it will require for the photosynthetic reaction. If you place strong light on your planted aquarium without adding a balanced amount of carbon dioxide, you will be more likely to encounter algae problems.