I can break down some of the terminology that can seem overwhelming at first and I’m pretty certain that everyone venturing in to
co2 has been as equally anxious.
Starting from the cylinder and working towards the tank.
Some people use paintball cylinders. Some like to use
co2 fire extinguishers, some like to use soda stream or branded commercial set ups. Branded commercial set ups tend to be smaller systems that can run out quicker and charge a lot for new cylinders or refills. If you buy a branded set up like JBL e.g I can guarantee you will end up upgrading at some point.
I shopped at Co2ART.com and purchased a cylinder regulator that fit the thread of a
co2 fire extinguisher. I can get easy refills for £5 at a local fire service place. My tank is small so refills last a long time. Maybe 3 months. I bought 2 x extinguishers and always had one full ready to go.
***Disclaimer*** Do your research on these cylinders and decide for yourself whether you want to modify a fire fighting device for aquarium use. Branded setups will come with safety standards and are intended for the purpose they were designed for.
You can buy dual or single stage regulators. Dual offer better valve control and likely smoother gas output but single is perfectly fine. On the cylinder you will want a solenoid which serves as an electrical shut of switch that can be plugged in to a timer. This enables you to switch the
co2 off and on at your preferred times. The regulator needle valve allows the gas to flow out of the cylinder the more you turn it the more gas flows. You will leave this open and in place at all times. If using a solenoid, the gas will stop at the solenoid when it is off and only begin to flow in to the air tubing and in to the tank when the solenoid is open. This set up saves you messing around to find your desired flow output every day which is dangerous for your fish.
Tubing is simple, it just needs to be
co2 resistant.
In the
co2 tubing line you can add a bubble counter. This will help you settle on a visual rate of flow that is suitable for your tank. They are small vessels with water in them so as the
co2 passes through the vessel it is shown as a bubble. This is not a universal unit for determining
co2 flow. All bubble counters are different and release different size bubbles. The rate is usually quoted as bubbles per second BPS or bubbles per minute BPM.
After leaving the bubble counter the
co2 will hit a an tank diffuser. Often made of a porous ceramic. Because of the tiny holes in the diffuser the
co2 will not pass until the correct diffuser working pressure is reached. This causes the flow to stop for some time. Your bubble rate in your counter will slow or stop. When the working pressure of the diffuser is achieved the
co2 will pass and the bubble counter will begin to release bubbles again. You will need to adjust the needle valve again at this point and set the final bubble rate in the counter. You must also ensure that the
co2 cylinder output pressure is high enough to over come the diffuser working pressure. Normally you can adjust the regulator output pressure usually a knob or turning screw on the front. Some regulators are factory set and can’t be adjusted.
To measure
co2 a drop checker can be used. Drop checkers allow
co2 to pass in to a chamber filled with a known solution of carbonates. The solution turns from blue usually to green when the quoted optimum level of 30ppm
co2 has been achieved. Though drop checkers are not really time so there is a delay until the colour reaches it’s final shade. This could be lime green which could indicate too much
co2 or light blue which will indicate too less. This stage will require you to be in the house all day to monitor the tank. Only when you have the optimum needle valve position, bubble rate and drop checker colour and you have observed the tank for the day to monitor fish health can you leave the tank with the system switched on.
Inline diffusers are used with canister filters and fit inline with the canister filter outflow tube which flows in to the tank. The diffuser sits inside a plastic vessel and water from the canister flows through the vessel. The
co2 line from the cylinder regulator goes on to the side of the vessel so that gas is pumped in to the flowing water as it passes. They offer better dissolution benefits and remove the tiny bubbles from the tank you get with a in tank diffuser.
Thats it for now. Hope this helps.
New to FW fish? First tank in a long time or EVER??? Need some info on keeping fish? 
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