CO2 is an important parameter in planted aquarium. Without CO2, plants will not be able to grow. To understand more about CO2, click here to read "CO2 for planted aquarium" by Josh Sim and Robertus. In this article, we want to demonstrate how easy it is to setup a CO2 system for your planted aquarium.

To begin, we need to ensure we have the following items. Some are optional but maybe useful to some aquarists. Let's go through the checklist so that you wont need to run to your aquarium shop 1/2 way during setup.

 List of equipment needed:

1. Pressurised CO2 cylinder. These stainless steel/ aluminum alloy cylinders can be purchase commericially. They comes in various capacities ranging from a few hundred grams to a few kilograms. There is a main valve on the pressurised CO2 cylinder to turn on the supply of CO2.

2. Pressure regulator (manual/automatic). Manual regulator is prone to unstable bps. It is because manual regulator does no step down the pressure from 800-1000 PSI to around 25-30 PSI like what the automatic did. Normaly manual regulator only have 1 pressure gauge to measure the tank pressure. Automatic regulator have 2 pressure gauge, one to measure the tank pressure, the other one to measure the output pressure.

3. Solenoid (optional). The type shown in the picture is regulator comes with a built in solenoid which can be used to cut off the CO2 when needed.

4. CO2 tubing. There are many types available commercially. Try not to use the transparent type used for normal airpumps as they might not be able to withstand the pressure and may degrade over time. The type shown in this picture is the type used for pneumatic application and is able to withstand high pressure.

5. Check valve (one way valve). These are many types of check valves in the market. Some are made of metal while others are made of plastic. There also one that made from glass. All of them serve the same function and pretty capable of doing the job. Please note there is an arrow on the check valve and during installation, it might be install in the direction of air flow. Be generous when installing check valve, you need to make sure no water enter the CO2 tank. Once water enter the tank, your tank is considered gone, the top-up company will reject your CO2 tank.

6. Bubble counter. There are various types sold in the market and all of them serve the same function. The type shown below have a built in check valve and tightening nuts at the both ends to fully secure the CO2 tubings.

7. Joint glass (optional). As the CO2 tubing is rigid, it is difficult to bend it over the edge of the tank. The joint glass helps to overcome this problem.

8. Internal/ External diffuser/CO2 reactor. There are various types of internal/ external diffuser sold in the market. The one shown below can diffuser very small bubble. However, it requires a higher pressure to force the CO2 out due to its dense ceramic construction.

This glass diffuser is the most commonly used diffuser. The working principle is similar to how a ceramic diffuser works. The only disadvantage is that glass is brittle so please handle it with care in case it breaks and injures yourself.

An inline diffuser as shown below can be placed outside the tank and is also very efficient in diffusing the CO2. As it is placed outside the tank, it makes your tank looks nicer without an additional piece of equipment. The minor setback from this inline diffuser is you require a cannister filter or a powerhead for it to work.

9. Drop checker (optional). Some aquarists use it to monitor the amount of diluted CO2 in the tank. Some aquarist simply dont bother.

10. Electronic timer. This is used to cut off the electrical supply so that you can turn off your CO2 supply. This is applicable only if you are using solenoid.

Please take note that your equipment/ items may look different from our pictures but as long as they serve the same function, it doesnt matter. Once you are done with the checklist, let's start to do the connection.

This is a typical CO2 connection layout:

CO2 tank -> Regulator -> Soleniod -> Check valve -> Bubble counter -> Check valve -> Internal/ external diffuser.

Simple? Well, it still sounds so confusing. Let's use pictures to illustrate:

Step 1) Install the pressure regulator onto the pressurized CO2 cylinder as shown and ensure the tightening knob is fully tighten.

Step 2) Next, connect one end of the tubing to your pressure regulator. Ensure you have fully tighten the securing knob on the pressure regulator else the tubing might drop off. Make sure you have enough length from the knob to the check valve. This is to cater water back flow.

Step 3) Connect the other end of the tubing to the inlet of the check valve. If you look at the check valve carefully, there is an arrow indicating the flow direction. Using this arrow, you determine which is the inlet and outlet of the check valve. Kindly ensure the check valve is correctly orientated.

Step 4) Connect the outlet of the check valve to the inlet of the bubble counter with a CO2 tubing. Ensure you fully tighten the securing knobs on the bubble counter to prevent the tubing from getting loosen. Kindly ensure the bubble counter is correctly orientated.

Step 5) Connect the outlet of the bubble counter to the inlet of the check valve with a CO2 tubing.

Step 6) Connect the outlet of the check valve to one side of the joint glass with a CO2 tubing and from the other side of the joint glass, connect to the internal/ external diffuser. There is no orientation for the joint glass as either side can be inlet/ outlet.

Step 7) Once all the connection are done, adjust your electronic timer to on/ off your CO2 supply. Plug in the solenoid socket into the electronic timer and then switch on the power supply

Step 8) Once it is done, switch on the main valve on the pressurized cylinder to turn on the CO2. When you open the main valve you should see the needle on  pressuse gauge move. The main gauge will indicate around 800 to 1000 psi depending on surounding temperature and if you are using automatic regualtor, you should see 25-30 psi on second presure gauge. When the main pressure gauge drop to around 100 psi, its mean time to top-up.

Step 9) After main valve open use soap bubble or shaving cream to check for leackage. Apply it to anny possible join, normally those metal join. Soap bubble or shaving cream is a good tool to find leackage. Another important thing is to check for back flow. Check it in the morning before the CO2 turn on, at which level does the water go up to. Eventhough you have check valve to prevent back flow but not all check valve build equal.  Some check valves are poorly design or maybe spoiled.

Step 10) Install the drop checker in your tank to monitor the amount of diffused CO2 in the water.