Aquarium DIY CO2 Kit: Citric Acid/Vinegar and Baking Soda

I had a spare 5 gallon tank and I had been toying with the idea of doing up a planted tank with fish, and going semi high-tech with a DIY CO2 kit. And some people might ask “Is DIY CO2 really worth the trouble?”, or frequently you will see on forums and FB groups that DIY CO2 is a waste of time.


Why I chose DIY instead of a pressurised CO2


  • Low initial cost
  • Ingredients can be purchased locally, and stocked up.
  • Ingredients are everyday item and can be used for other purposes. (Your wife will never complain if you stock them up!)
  • No down time. Whenever I run out of ingredients, I can get the system up and running away shortly.
  • Shoe Leather Cost. Refilling CO2 tank at the nearest LFS is 16km away. Imagine the time and fuel cost.
  • You may not be free the following day when your CO2 runs out. You may not even be free for the entire week!


  • Low capacity compared to Pressurised System’s 2 month running time. (unless it’s the high pressure DIY CO2 canister)
  • Low CO2 pressure. You will find atomizer impossible to be used with DIY setup.(unless it’s the high pressure DIY CO2 canister)
  • Inconsistent CO2 releases. Sometimes when I leave my house, it is doing a respectable 4~5 bubbles per CO2. But when I got home, it is doing maybe 1~2 bubbles per second.(unless it’s the high pressure DIY CO2 canister)
  • Need to replenish the bottles and it can get a little messy sometimes (but much easier than yeast/baking soda formula)(unless it’s the high pressure DIY CO2 canister)
  • Higher running cost in the super long run. (unless it’s the high pressure DIY CO2 canister)

The high pressure DIY CO2 Canister has non of the inherited problems of the two bottle system


Find out more about the latest High Pressure DIY System

Choosing your preferred kit

After researching online for days I settled for a DIY CO2 kit that is quite popular on Aliexpress and Amazon. Cost just around US$22 with free international shipping from AliExpress.

1st Generation

2nd Generation

Gen 2 AB Bottle DIY CO2

The single greatest advantage of this kit is you can actually shut it off at night! It will not explode like the yeast + baking soda recipe. In addition, the reaction is immediate. Squeeze the bottle, vinegar got pumped into baking soda, and you get CO2 and pressure build-up immediately. No need to wait for fermentation.

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There are cheaper variants around but I settled on this because it has a brace that can secure the soda bottles so it is easier to carry around when doing maintenance. And it looks much cleaner.

The kit came with all the tubes attached so there is really nothing else to setup. The only thing you need to do is to screw the soda bottles in and attached the outlet tube to the kit and to your bubble counter/diffuser.

Update: May 2019

Improved Version: Aluminium Kit with Solenoid and Bubble Counter

Singapore reader: Get it from for SGD21 with free shipping

Aluminium CO2 Kit $30 with free shipping

This kit was released by ZRDR Aquarium and is constructed of aluminium! Basic kit comes with just the brace, pressure gauge, and valve control and cost just $15 with free worldwide shipping!! WTF!?!. Kit B comes with bubble counter and cost $18 with free shipping as well. Complete kit comes with additional electric solenoid!

Citric Acid or Vinegar?

Either citric acid or vinegar will work. From my experience, citric acid is a more concentrated acid than vinegar and it is less pungent.

Vinegar on the other hand does not require mixing and shaking. It is also cheaper and easier to come by. Citric acid sold in supermarket can be extremely expensive.

If you decide on using citric acid, the formula remains the same as recommended.

If you want to try vinegar as a substitute, here’s the formula:

Baking Soda 400g +
Man-made/artificial vinegar 1L

That’s it!

You do not need to mix the vinegar with any water.

You do not need to mix the baking soda with water as well!

The cost is well under US$3. The 400g baking soda cost me just US$1.30 and I purchased a 5L white vinegar at my local supermarket for a mere US$4. My latest mix has past 10 days and I predict it can surpass 15 days, no sweat. If I increase the baking soda to 800g I am pretty certain it can last 1 month.

Singapore Reader Note: So far I discovered that only Giants @ Vivocity sells the 5L white vinegar. You can still get the 3L pack from a reasonable size Giants. The smaller Giants are only selling small bottles. Citric can be purchased from Poon Huat. They are a bakery chain stores and 500g citric acid powder cost about SGD$5.

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How To Set Up – Using Vinegar

You will need to get two empty soda bottles. I am using 1.5L bottles. They MUST be from soda drinks. From what I learned, soda bottles are manufactured to withstand higher pressure than your normal non-carbonated drinks.

Step 1

Pour 400g of baking soda powder into one bottle. No need to mix with water. Just raw powder form. (Okay, 400g maybe too much! 200g~300g will be perfect for smaller bottles.)

Step 2

Screw the bottle containing the baking soda into the socket with the tube that DOES NOT have the ball-head. Make sure it is tight. Be careful not to over screw and risk damaging the threads and O-ring

Step 3

Pour 1L of vinegar into the second bottle. You can adjust the amount of vinegar according to your bottle size or needs. BUT DO NOT FILL MORE THAN 1L or you will cause the baking soda bottle to be overfilled later on, and the vinegar/water mixture will end up being pump into your tank!

Step 4

Screw the bottle containing the vinegar into the socket with the tube that has the ball-head. Make sure it is tight as well.

Step 5

Attach one end of the long tubing to the outlet that is on the screw valve.

Step 6

Next, estimate how long you will need to run the tube from your bottles to the tank. Cut off the excess.

Step 7

Then cut the tubes into sections so you can connect your check-valve, bubble counters, and diffuser.

How to Start the reaction

Once everything is connected you are ready to start the reaction.

Step 1

Make sure the outlet valve is open. Then give the bottle with the vinegar bottle a really hard squeeze.

Step 2

When the vinegar touches the baking soda powder, the reaction is immediate!

Step 3

You will need to give the vinegar bottle a handful more squeezes before the reaction can be self-sustained.

Step 4
  1. Once you see vinegar started flowing without your intervention it is time to shut the valve.
Step 5

Now let the pressure build up. Keep squeezing the vinegar bottle until you cannot squeeze any more. Yes! That’s how much pressure we need to build up. I would take a break and come back again later.

Step 6

The pressure gauge is a bit tiny and I have trouble reading it under dim light some times. Getting old. At 1.5 reading you can slowly release the valve.

Step 7

If everything went well, you can see the diffuser fizzling immediately.

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If even after releasing the valve all the way until it came out and there is still nothing coming out of the the diffuser, DO NOT PANIC!

Insufficient acid injection

Sometimes the reaction is not sufficient. Unscrew the bottle containing the baking soda SLOWLY but not completely. Keep unscrewing slowly until you hear gas escaping hizz. Immediately vinegar will be drawn into the baking soda bottle resulting in more reaction and more CO2. Screw the baking soda bottle back immediately.

Pressure insufficient to push through check valve

The DIY CO2 pressure is kinda low for some check-valve. Loosen the check-valve. Keep loosening. And then you will get a rush of CO2 into your bubble counter! The feeling will be tremendous! Lol.

If your bubble counter comes with check-valve, loosen until water starts to leak from it. Then gently tighten it until there is no more leak. If there is still no movement, use your finger to give the bubble counter a good knock.

I will try to upload some videos later on. Let me know if this works 😉

Acid bottle finished just after 1 day

Well when you woke up to find your citric acid solution gone over to the baking soda solution bottle overnight it usually means a leak has developed. The most likely culprit is the rubber O ring was torn and could not keep the CO2 trap.

Fragile O Ring

Unscrew your bottle and inspect the transparent O ring. This O ring is extremely fragile and can tear when screwing your bottle in. It can also becomes dry and disintegrate easily when exposed to citric acid.

Remember to always rinse it well during every bottle change, or best if you can soak it in water.

The problem is known to the manufacturer and as such the kit will come with a couple of spare O rings.

How to squeeze a few more days of CO2 out of your kit

Towards the end of your CO2 generation, you can shake your bottle a bit and that will stir up any unused baking soda and create more CO2.

And also, use a reactor! Towards the end of your CO2 production the pressure will become too low to power your diffuser.

By using a CO2 reactor you the remaining pressure can still give you a few more days of usage!