Co2 diffusion in the planted tank

Plants, like all living things, require proper nutrients to thrive. While animals hunt for food, plants depend fully on environment for their basic nutrients for their survival and growth. Photosynthesis, the driving mechanism for plant growth, requires CO2 and light for energy to drive chemical reactions. Besides, various other elements are also required during photosynthesis for creating carbohydrates.


Plants store these carbohydrates and use it later for the growth. A specific light energy threshold is required for the process of photosynthesis, which will not occur if the light is not bright enough. Photosynthesis will run faster and faster beyond that threshold. Depending on the types of plants and depth of aquarium, around 2-3 watts per gallon of fluorescent light is recommended. The required light levels cannot be measured accurately by using watts per gallon. But, it is the only reliable measurement available for aquarists. As mentioned earlier, various nutrients are required for photosynthesis. Short supply of even a single nutrient will limit the rate of photosynthesis.

A typical aquarium is deficient in both iron (Fe) and CO2 with respect to optimum levels. Lots of trace element products are available in the market for meeting the requirements of iron and other trace elements although many manufacturers produce also bottles fill ed only with Iron. In order to boost the concentration of CO2 in a planted tank, CO2 injection is the best way. Here comes the importance of CO2 diffusers.

CO2 Diffusion: Is it Harmful to Fish?

CO2, in high concentrations, can block the respiration of CO2 from fish gill. This will cause the starvation of oxygen. A certain level of CO2 exists in all aquariums. Fishes exhale CO2 through the process of respiration. However, this is not enough for live aquatic plants in an aquarium, as in nature there is much more of this gas in the water.

If you want to attain a certain level of lush plant growth, you have to add CO2 mechanically to the planted aquarium. You are aware that plants require an environment with certain concentration of dissolved CO2. This level is around 10 to 15 ppm (part per million). You should strictly keep this value as constant as possible. A high amount of dissolved CO2 can harm your fishes and other invertebrates that live in your aquarium. If you are able to keep it below 30ppm, you will be on the safer side. Depletion of CO2 can cause various problems in your planted tank. Paling in the stems and leaves, and stunted growth of plants are the most notable problems. If the level of CO2 remains low for long, it will lead to the death of plants in your planted tanks.

Aquarium plants also start getting lime deposits on their leaves. Moreover, dissolved carbon dioxide (CO2) becomes carbonic acid in water. As a result, the depleted levels of pH of your tank will decrease, which creates serious consequences for plants and fishes in your aquarium. Both plants and fishes will have increased susceptibility to diseases in rising or decreasing  pH levels. Besides, you can also expect the algal growth due to increasingly low CO2 levels. It will cause lots of other problems, which include ammonia poisoning. In order to inject CO2 in a planted aquarium, a wide range of CO2 equipment is available in almost all aquarium stores.

What CO2 diffusion methods are available on the market?

People are using these products for their planted aquariums. You can supplement carbon dioxide in your planted tank in a number of ways. Gas or liquid injection is most famous among them. You can administer carbon (in gaseous form) in three ways, pressurized system, yeast based and aerosol. The third one is the cheapest CO2 alternative and it is useful for smaller tanks. Yeast based diffusion is the most uncontrollable and inefficient way of getting CO2 into a planted aquarium. Pressurized CO2 systems are considered as the easiest and best option to deliver adequate level of CO2 in your planted aquarium. These are reliable and consistent, but these systems are more expensive. However, you will get the best quality CO2 diffuser for your plants at an affordable cost at CO2Art.

As we are specialized with pressurized systems, let us present you what diffusers can be found in our offer:

-In line diffusers

The Inline diffuser we have in our offer comes in two sizes: 12/16 and 16/22. A great advantage of this quality product is that it's an external diffuser which means less equipment inside the tank. The in line diffusers are recommened specially for larger tanks. Another advantage of this inline diffuser is that you can purchase the replacement ceramic membrane seperately.

-In tank diffusers

In tank diffuser is a diffuser that is places inside the aquarium. We have to models of in tank diffuser in our offer and it's your choice which one will be more suitable for your set up.

The first is Bazooka Flux Diffuser which comes in two sizes: small (for tanks below 250l) and large (for tanks above 250l). As CO2 bubbles pass through the porous diffuser, they are diffused into streams of tiny bubbles. With increased surface area, the fine bubbles of CO2 are readily dissolved into the aquarium water, increasing the saturation of CO2 in the aquarium ecosystem.

The second in tank diffuser is the IO Diffuser which comes in two versions: acrylic and stainless steel and each in two sizes: small (for tanks below 150l) and large (for tanks above 150l). The material that it's made of is the matter of aesthetics. Stainless steel diffuser looks more elegant while the acrylic diffuser is white and delicate. The advantage of this model is that it comes with a replacement ceramic ring that can be also purchased separately. Carbon dioxide is injected into the aquarium through this ring, diffusing a fine mist of bubbles in the aquarium water. It is recommended that you set the high pressure on your regulator to a minimum of 2 bar as a starting point. Don't worry about big bubbles coming from the diffuser in the first few hours. The ring pours need to fill with water and then the visible bubbles will have optimal size.

The common advantage of our diffusers is their easy setup. All instrucions are provided on our website and our Support Team is happy to help you with any problem.

In all cases, it's important to use tubing resistant to CO2. Find the best tubing on our site available in 5 colours: clear, black, blue, green and silver.

How will I know how much CO2 should be injected into the water?

We recommend you to try the drop checker method. The drop checker method will allow you to measure the CO2 levels in your tank constantly. Once it's placed inside the aquarium, the colour of the water in glass indicates the level of CO2. Then it's blue- then there is too little carbon dioxide in the tank; when it's green- we can say that the amount od CO2 in the tank has optimum level (safe for fish and plants). If the water is yellow- the level of CO2 is too high which is very harmul for aquarium fish. This method will be very effective for large tanks as well as for smaller aquariums. It's also worth underlining that it's best to purchase drop checker solution from a reliable source. There are many recipies on Internet forums how to do it yourself but be aware that mixing a well-calibrated fluid is not easy. We encourage you to use our product which is perfectly calibrated to read accurate CO2 levels.

Other method is to measure KH and and pH with a test kit. Then you need to find a table and the crossing of these parameters will be the amount of the gas is needed for healthy plant growth and safe for fish.

Another method is the bubble counter method. The bubble counter allows you to visually control the amount of CO2 injected into the tank. Changing the settings with the precision needle valve is almost immediately visible in the bubble counter, much faster than the diffuser reacts. See the premium bubble counters we have in our offer or trust our regulators with integrated bubble counter. Remember to refill the water in the bubble counter regularly.


Choosing the quality equipment is a key factor in future aquarium maintanance. Trust only reliable brands. Consider all pros and cons of In-tank and In-line diffusers before purchasing any. CO2 injection will completely change your aquariums appearance. Plants grow simply faster and healthier. Moreover, the colouration of the plants is more intense with CO2 fertilising. You'll see the difference with the blink of an eye. Ultra red red plants and deep green carpet plants in the tank are one of them.