Table of Contents
What is CO2 anyway?
This is where it gets a bit chemical again. In this context we also refer to our Guide to chemistry there. There we have explained many terms in more detail.
Co2 is a compound of carbon and oxygen and is not only found in aquarium water, but also in the air. In the aquarium it is closely related to the PH value and the carbonate hardness KG. O2 also works closely together.
What do aquatic plants need to grow?
Of course, CO2 will not be enough here to make aquatic plants look magnificent. Nevertheless, plants need CO2 for what is known as photosynthesis. This in turn is important in order to also produce O2, i.e. oxygen. O2 is required by the fish. One can also speak of a cycle here. In addition, aquatic plants need a lot more nutrients. Be it iron or phosphate. But the right water temperature and the right light are also required. Here is an overview of what aquatic plants need:
- The perfect light / light energy – More on that in Lighting guide
- The appropriate water parameters such as PH, KH or also Temperature
- The right mineral nutrients - iron, CO2, nitrogen, phosphate, potassium, sulphur, calcium, magnesium, copper, zinc, manganese etc.
- The optimal floor – more on that in Advice on soil in the aquarium
These nutrients are not only absorbed by the plants through the roots, but also through the leaves. In contrast to land plants, aquatic plants can absorb nutrients from all parts.
What is the CO2 content in my water? How do I measure the CO2 content?
Measuring the CO2 in the water is not as easy as measuring the KH or GH value. So-called droplet tests are usually used there. This doesn't really work with the Co2. Here the trade relies on the use of long-term tests with indicator liquids. In addition, manufacturers like Tetra but also JBL, Sera. Aqua Rebell or Dennerle have developed special long-term tests that tell you whether you have a good CO2 value or a rather bad CO2 value. An exact determination of mg/l will not be possible with this either.
There is another way of measuring or calculating. You can also calculate the CO2 content. The values PH and KH are required for this. With a corresponding formula, one can calculate the current CO2 content dissolved in the water. Unfortunately, there are also disadvantages here, because many other values still influence the CO2 and therefore the calculation via PH and KH (carbonate hardness) is not recommended.
Nevertheless, we provide the formula for you here: CO2 = KH/2.8 * 10^(7.91-pH). an appropriate one Of course you can also find CO2 calculators with us.
Another method is to determine using a table, which can also be found very often on the Internet. The CO2 value is also determined here based on the KG and PH values and can be easily read off. There are also colored markings indicating whether this is in the green, red or yellow area.
Let's summarize:
The ways of determining the CO2 content in the aquarium
- Measure CO2 with an endurance test and indicator liquids
- Calculate CO2 using a formula
- Calculate CO2 using PH value and carbonate hardness KH
- Read CO2 from a table using PH and KH
Too much CO2 in the water? What is the benchmark
But you should be careful if you get the accumulation of Co2 in the water above a value that the plants can no longer absorb. Then it becomes dangerous for the respiratory organs of the fish. Above 30mg/l currently seems to be a value that is seen as the limit for accumulation. Many manufacturers and also aquarists recommend a guide value of around 25 mg/l CO2.
Of course, it also depends on how many plants are in a tank. Not every aquarium requires the same amount of Co2. Heavily planted tanks require significantly more CO2 than tanks that are hardly planted at all. It is therefore difficult to set a general guideline at all. Nevertheless, one can assume around 20 - 30 mg/l in a community aquarium in the freshwater area.
Fish are very sensitive to excessive CO2 levels and this can even lead to mass deaths. Unfortunately, one reads this again and again from aquarists that all fish were dead in the morning. That's why it's important to pay close attention to what happens with the CO2, especially at night. At night, less CO2 or no CO2 is used by the plants at all, since no photosynthesis takes place due to the lack of light. We therefore recommend turning off the system overnight. In order to be able to do this, some technical requirements are necessary. But more on that later.
CO2 fertilization against algae
CO2 fertilization not only has its advantages in the area of aquatic plants, but also has a very positive effect on algae growth. By enriching the aquarium water with Co2, the algae will also go to the bottom. The reason here is the nutrient withdrawal due to the multiple use of the plants. Thus, the algae lack the most important thing to reproduce. Therefore, if you have an algae problem, you should ensure that you have enough aquatic plants in your aquarium, preferably fast-growing ones.
How does a CO2 system work?
There are different models from the manufacturers, although the basic functionality is almost always the same. CO2 is either produced or stored in a container. During storage, the CO2 gas is stored in a pressure vessel. This has a similar shape to a propane or butane gas cylinder but is usually smaller. This gas is then passed into the aquarium water.
But in order to achieve efficiency, it is also necessary to create a good distribution and solution in the aquarium water. There are so-called diffusers for this. They ensure that the individual gas bubbles can slowly dissolve in the water. The design of these diffusers is quite different. Usually, however, they are spirals, where the individual bubbles run from bottom to top and thus become smaller and smaller. Ideally, nothing should arrive at the top, then the CO2 would be very well dissolved. Some manufacturers also use the term pinball for diffusers. Here the gas does not run upwards in a spiral, but in a staircase.
But if you were to connect the compressed gas bottle directly to a diffuser, the gas would escape in one fell swoop. That's why you have to be able to control and regulate the system somehow. A so-called pressure reducer is used for this purpose. It ensures that the gas can only escape under a certain pressure. Most of these pressure reducers have two pressure gauges. One shows the bottle pressure in bar and the other can adjust the evasive pressure using a regulator. This is usually in the range between 1-3 bar and the bottle pressure can be up to 2 bar depending on the filling of the Co80 bottle. So you will not get along without a pressure reducer.
The CO2 hose, which by the way should also be a special one, is connected to the pressure reducer. He should not let any Co2 gas escape.
These parts would already be sufficient to introduce CO2 into the aquarium in a controlled manner. But if you want it a little more comfortable, you can use two other facilities. The first option is an electronically operated solenoid valve that can shut off the supply of CO2. This can be necessary, for example, if you want to control the initiation with a timer. It would thus be possible that no CO2 flows into the aquarium at night, which can make sense.
Another facility is the permanent measurement of the pH value. The PH value is influenced accordingly depending on the CO2 in the water. Basically, one can say that the more dissolved CO2 there is in the water, the lower the PH value. Of course, this only works up to a certain range.[the_ad id="1019″]
There are also probes and control units on the market that measure this permanently. With these control units, it is then also possible to switch the solenoid valve and thus customize the enrichment.
who the same If you want to supply several aquariums with CO2, you will need additional components. Depending on the implementation, these can be distributors or branches that simply direct the gas to other basins. There are also special distributors such as the JBL Proflora duo or others. However, we advise you to be careful what you do here. It can quickly happen that the conditions and requirements in the individual pools are different.
Therefore, this should only be used by experts and not necessarily by beginners.
Components of a CO2 system:
- Compressed gas tanks in various sizes
- pressure reducer
- CO2 hose
- magnetic valve
- Regulations on the PH value
- diffuser or flipper
- Accessories such as attachment and Co
- Distributors and branches for several aquariums
How do I set up a Co2 system correctly?
How much does a CO2 system cost?
Now let's look at the costs. Here we can only make general statements, since depending on the type and scope of the system, the costs can fluctuate extremely.
Probably the cheapest option is either to build a Bio Co2 system yourself or to use a set in a specialist shop. You can find out how to build such a system yourself below. The purchase of a bio CO2 system is already possible for around 30 euros, be it from Dennerle or from JBL.
If you want a system with a compressed gas tank, you have to pay a little more. Here it starts from about 100 euros. Most of the time, however, disposable gas containers are included, which we would strongly advise against. You should get a at least 2 kg CO2 bottle for around 70 euros and is thus also prepared for the future. These can always be refilled in the aquarium trade. The maintenance costs are therefore significantly lower.
How much does an aquarium cost to maintain?
If you want a regulated system with PH probe and control unit, you have to add a little more. Nothing much will be possible here for less than around 200 euros.
Of course, the prices also depend on the capacity of the aquarium. A system for a 60 liter tank is significantly cheaper than a system for a 500 liter aquarium. In the case of the latter, you will no longer be able to get by with a BIO filing system.
When should you start using a CO2 system?
It depends, one could answer spontaneously here. Especially if you have an increased need for CO2 in your tank. When is this the case? Of course, if you have a lot of plants. However, this also depends on the existing PH value from the water pipe. The water movement and thus the expulsion of the CO2 is also an essential factor. If you have a high water movement, the Co2 will evaporate faster.
Another reason can also be the influence on the PH value to prevent water treatment, for example with osmosis. You can find out more about water treatment and osmosis or reverse osmosis systems here.
Are there alternatives to the CO2 system?
Yes! Basically, you can build your own Bio Co2 system. There are also chemical supplements in specialist shops, which are supposed to increase the CO2 content in the water. We advise against chemical preparations.
Build your own organic CO2 system
This is also possible, but will become problematic at a certain size. Basically, you have to ensure a fermentation process in a bottle, which then generates CO2 through fermentation. The fermentation solution is usually created with yeast or baking yeast and sugar. But it is also already available in bottles from specialist retailers. The fermentation process can therefore produce CO2. With such a system, it is usually difficult to regulate. Nevertheless, it makes sense, especially for smaller tanks and low demand. If you want to know exactly how to build such a Co2 system, you should watch this video. We will also write a detailed guide on this shortly:
Oxydators as a replacement for CO2 systems?
First you have to explain what a oxidizer is. Again and again this is associated with CO2 fertilization. But this is wrong, because an oxidizer does not produce CO2 but pure oxygen and rather ensures that the carbon dioxide is expelled from the water. It certainly has its advantages, but not when it comes to enriching the water with CO2. Here is a nice explanatory video about the Oxydator. So its function should be clear: