First attempt at DIY CO2

More of an experiment and a bit of fun than anything but today decided to tiptoe into the world of CO2. I didn’t want to spend any money on disposables or more keen diy setups so I just used what I had in the shed.

My tank consists of all easy care plants that don’t really need supplementary CO2, but I thought a low increase won’t hurt anything.

So I estimated my current dissolved CO2 level online using aquariuminfo’s calculator. I used a recently calibrated digital PH meter and API test strips to attain the PH and KH.


I used the ingredients ratios and bps advice from (https://www.cichlid-forum.com/articles/diy_co2.php) and bits and bobs in the shed from a BBS hatchery project to build the Simple setup.
I’ve plumbed the output line from the bottle, via check valve into the Venturi input on the spray bar. This spray bar is positioned underneath the output flow from the canister filter which I hope gives me the best chance of getting a bit of co2 mixed into the water. There is a variable air flow valve shut tight put there to close the second cap hole and can be opened if I need to release pressure for any reason.



The ratios of sugar yeast and water should produce 1 bps Co2 by tomorrow and last up to a month of the guide is right.

Target bps on the calculator was 0.4-0.8 depending on diffusion efficiency so with my ultra low efficiency setup my 1bps won’t harm anything. I’m hoping to achieve 10-20ppm dissolved co2 from my current 6.5.
If this setup allows this I will be amazed and very happy haha.

I will continue to monitor PH and KH incase anything goes astray and update progress/results as and when!

I've had good results with the yeast+sugar co2 combo in the past. If you search a user @SuperColey1 on here he put together a good thread a while ago.
More recently I've been impressed by the citric acid+bicarb method that is setup in two separate bottles. With this method, the reaction can be controlled, whereas with the yeast, the reaction is constant and can be an issue at night when the lights are off and we don't want to be injecting co2.
The citric acid setup relies on pressure, when the pressure drops in one of the bottles, more mixture is drawn across which results in a reaction and more co2 being produced.

mbsqw1d said:

I've had good results with the yeast+sugar co2 combo in the past. If you search a user @SuperColey1 on here he put together a good thread a while ago.
More recently I've been impressed by the citric acid+bicarb method that is setup in two separate bottles. With this method, the reaction can be controlled, whereas with the yeast, the reaction is constant and can be an issue at night when the lights are off and we don't want to be injecting co2.
The citric acid setup relies on pressure, when the pressure drops in one of the bottles, more mixture is drawn across which results in a reaction and more co2 being produced.

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I’ll look into both thanks!
Yeast version was chosen just because I had everything here to do it but I’ll be sure to check out the citric acid version next. I’m not going to be spending any money on co2 until I have a tank and plants that actually warrant it ha.

My plan for night time is to crimp the input line and open the pressure release line - would be daft of me to risk a ph drop should it decide to ramp up overnight.

I will be interested to see if you notice any difference in your plants. I set up the same system and ran it for about 6 months. I decided that I couldn't really tell if it was helping or not so in the end gave up on it. Keep us informed how you get on please.

itiwhetu said:

I will be interested to see if you notice any difference in your plants. I set up the same system and ran it for about 6 months. I decided that I couldn't really tell if it was helping or not so in the end gave up on it. Keep us informed how you get on please.

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I will let you know! Initial test is to see if I can get the ph to drop over the next couple of weeks indicating the rise in dissolved co2 providing KH remains constant. Unless I can achieve this I will sack this design in and move on to mk2.

Gemmsy said:

I will let you know! Initial test is to see if I can get the ph to drop over the next couple of weeks indicating the rise in dissolved co2 providing KH remains constant. Unless I can achieve this I will sack this design in and move on to mk2.

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My system was on an acid tank and didn't notice any real shift in pH

Totally off topic, but you photos seem to show that the tank overhangs the stand/table by a few inches. if it really does overhang, you need to do something asap as this could cause the bottom glass to crack. The entire base needs to be supported, either by all of it being on the stand or by using a thick piece of wood bigger than the base of the tank between the tank and the stand.

I can't tell from the photos whether there is one or not, but a flat bottomed tank also needs a foam base mat or polystyrene under the tank.

essjay said:

Totally off topic, but you photos seem to show that the tank overhangs the stand/table by a few inches. if it really does overhang, you need to do something asap as this could cause the bottom glass to crack. The entire base needs to be supported, either by all of it being on the stand or by using a thick piece of wood bigger than the base of the tank between the tank and the stand.

I can't tell from the photos whether there is one or not, but a flat bottomed tank also needs a foam base mat or polystyrene under the tank.

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All in progress but thanks for the heads up . Just moved them over from my parents so they’re on a spare table while I build a quick frame.

That's good to know I just had visions of you finding a cracked tank.

Which diffuser are you using? I've noticed a big difference in them, some requiring much more pressure than others.

mbsqw1d said:

Which diffuser are you using? I've noticed a big difference in them, some requiring much more pressure than others.

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None just yet, I don’t own one and it was a ‘spend nothing’ project to start with... So I’ve just plumbed straight into the Venturi port on the spray bar of an old filter. This should need next to no pressure to get going. Once it actually starts kicking out some gas, still waiting at the moment 24 hours in.
I’ve been looking at the bicarb and acid setup for the next go to be honest, looks like it’s easier to achieve constant pressure and more of it/for longer.

Update: got very fed up with waiting for a bubble. Set about researching common issues and went in depth on checking for leaks, none found. Then found a way to test the yeast (as it was one of three pots found in the cupboard ) it was dead. As was the next. However the newest one found at the back tested ok .

It’s not new yeast so I’m still not overly confident after the last 2 days of staring at a bottle... but I’ve set it up again just now with the best tested yeast I had and upped the rate of yeast from 1/2 tsp to 2.5tsp to offset the cell viability issue I read about.
1tsp bicarb soda
2 cups sugar

Also added a sort of diffuser so I can see the bubbles easier for BPS measurement.
Let’s see how this goes!

We have bubbles!!! Yeast bottle looks completely different, foamy on top and bottle is pressurised. Bubble count is only about one in 20 seconds at the moment but it is only 3 hours in and it’s progress! Very rewarding. The make shift ‘spray bar diffuser’ looks to be doing a good job at making micro bubbles too!

I have switched off the lights and opened relief valve for the night. Looking forward to counting bubbles tomorrow!

Good to hear you're having fun with it I think that's why I enjoyed diy approach so much. Buying stuff of the shelf and switching it on is boring. Yeh, it might do the job perfectly straight away, but I find theres fun and learning to be had from building stuff yourself. It may well progress to a pressurised system in the future, but even then, I imagine you'll go the diy route on that too. Good on you

You can also take into consideration the optimal temperature that yeast is most active at. I never did this, but I considered sitting the bottles in a container of water that could be heated slightly by an aquarium heater during the day to warm the yeast up a little.

Exactly my thoughts! I would be bored pretty quick otherwise anyway haha. I am very much enjoying it .

I have thought about that to be honest! The new stand will be built on Saturday with any luck then I should have room for a few bottles sat in a tub but we shall see. I thought it might make it a wet job changing bottles though, also first I’ll have to see how much it makes at room temp as I really shouldn’t need much co2.

This morning when I was unknowingly struggling with that dead yeast I had the bottle wrapped in foil with two ‘instant hand warmer’ sachets from skiing stuffed down the side haha I was getting desperate haha.