Planted tanks can be some of the most beautiful aquariums, and live aquatic plants can benefit fish too. Plants definitely grow better with the addition of CO2, but some plants don’t need additional CO2 at all. A thriving, healthy planted aquarium can be created without CO2, as long as you choose the right plants, and light it accordingly.
It’s all about energy
Planted tanks can be divided into different energy levels, depending on their lighting. Brightly lit tanks are termed as high energy, and need strong water flow, CO2, daily fertiliser and lots of water changes.
Medium energy tanks with medium levels of light require less CO2, fertiliser and water changes because the lower light levels promote less photosynthesis than high energy. And low energy tanks with even less lighting require less fertiliser, fewer water changes, and no CO2. This is all because the plants are growing more slowly.
Low energy planted tanks are the best ones to set up if you definitely want to set up a planted tank without CO2. It will cost you less to set up and run too!
Standard stock lighting is fine for a low energy planted tank, so the lighting included in any Juwel, Fluval, Tetra, Eheim, Ciano, Aqua One or Aqua El tank will be fine to get started. The temptation will always be to add more light as many aquarists rightly think this is the most important factor for any plant. But increase the light and you will increase plant metabolism and the need for more fertiliser and CO2.
If you have bright light only and don’t make up the other two important parts of the plant growth triangle, the result will be algae. Plug the lighting into a plug-in timer and have it on for a fixed eight hours per day.
Substrate for the CO2 free planted tank should be as for one with CO2, i.e as nutritious as possible. Choose from aquatic soil used on its own, to a layer of substrate fertiliser under the gravel, to fertiliser balls pushed into the gravel. The deeper the substrate layer the better, with a minimum depth of 2”/5cm.
Flow does not have to be high in a low energy planted aquarium, so an internal canister filter will be fine. An external canister filter placed in the cabinet underneath will be even better, and if you don’t want to see the heater in the tank spoiling the aquascape, opt for a filter with built in heater.
Although the demands of the plants are less in terms of nutrient volume uptake, they still need a complete range of nutrients from a quality liquid fertiliser. Either add weekly after a weekly water change, or divide weekly dosage recommendations by seven and dose daily.
Plant species choice
Plant nurseries may divide their plant portfolio into Easy, Medium and Advanced. Choose from the extensive Easy range of plants when running a low energy planted tank without CO2 and you stand the best chance of success. Low energy tanks don’t have to miss out on all the best plants and there is still a huge range of suitable genera available including Anubias, Bacopa, Bucephalandra, Ceratophyllum, Cryptocoryne, Echinodorus, Hygrophila, Lobelia, Ludwigia, Microsorum, Sagittaria, Staurogyne, Vallisneria and more.
Choose the right plants in the first place which are strong, healthy and free of algae, fertilise regularly and don’t use too much light, and you can have a successful planted aquarium without CO2.