CO2 Alternatives?

[Garrett Johns]

Hey guys! Crazy idea, but do you think adding carbonated water (like club soda) to a fish tank would have the same effect as diffusing co2? I feel like it could work unless there’s something toxic in it I haven’t considered. Thoughts? 

[Fish Folk]

I think this was how Takashi Amano originally discovered the effects of CO2 on plants in an aquarium.

This page purports to be a facsimile of an article he wrote for TFH in 1992.

If you do this, it will not really work much. It's easy to crash the tank, and you must understand that plants need low, slow, and consistent CO2 to thrive.

But I want to encourage you! If you've just stumbled onto this thought yourself . . . you're following in the footsteps of the greatest aquascaper the world has ever known.

Watch this trailer: 

Learn more here.

Cheers!

 

[CT_]

Heh, I've thought about the same thing too.  As fish folk said you'd have to do it pretty slow and continuously. 

 

One thing that I think should work but I'm not sure anyone has tried, is to add a bicarbonate salt and an acid into their tank.  it should form CO2 but salts would also accumulate so you'd have to do more water changes (not sure if that means every hour or every week, I haven't done the math).

I think for a bicarbonate salt potassium bicarbonate would be a good choice as the K would be taken up by plants.

For an acid sulfuric acid would add sulfates, which plants need, so that could work, I forget if sulfates contribute to algae though. 

I think acetic acid is another option.  I /think/ plants can use the acetate left over.

 

I'd love for someone to try this, maybe without fish in until its shown it wouldn't spike co2 too high.  would be fun to try out with a couple 5g buckets, desk lamps and a high CO2 plant.  I don't have a good way to know if it ODs co2 though.

[DShelton]

On 6/30/2021 at 2:45 AM, CT_ said:

One thing that I think should work but I'm not sure anyone has tried, is to add a bicarbonate salt and an acid into their tank.  it should form CO2 but salts would also accumulate so you'd have to do more water changes (not sure if that means every hour or every week, I haven't done the math).

There are some great DIY systems that do just this. The reactants are usually citric acid and sodium bicarbonate. They work by siphon and sucking one reactant (citric acid) into a vessel containing the bicarbonate, producing CO2. With systems like this, since they work off of the siphon, you can control the reaction by shutting off the CO2 flow to the tank (i.e. manually with a valve, or automatically with a solenoid).

There are  a couple of DIY ways to do this, one using a manifold and solenoid:

https://www.dudegrows.com/my-diy-co2-setup/

 

Another way is to use some 2 port bottle caps for 2l soda bottles, a pressure gauge. a valve and some Tygon® tubing. Wikihow has a great article, and the kits are cheap on amazon or fleabay.

https://www.wikihow.com/Make-a-CO2-Reactor-for-an-Aquarium

 

There is also a commercial stainless steel bottle that you can buy, mix the acid/water/bicarbonate in the bottle, and the reaction pressures the stainless bottle, it is then controlled with a regulator and a solenoid like a traditional CO2 bottle. I think both Dennerle and JBL make one, but there is an FZone one on amazon that is cheaper than the big brands.

https://www.amazon.com/FZONE-Aquarium-Generator-Regulator-Diffuser/dp/B08ZLVQ5L5

 

These systems are cheaper than commercial CO2 systems, and refilling them is pretty cheap too. Both the citric acid and the bicarbonate are really cheap in bulk. I used a system like the one shown on the wikihow site for a few years on a 60cm tank and had to change the reactants every three weeks or so.

[NanoNano]

I see references on Reddit's r/plantedtanks of people using yeast somehow as a Co2 source.  Could I ask someone to explain that option as well?

[DShelton]

On 6/30/2021 at 9:10 PM, NanoNano said:

I see references on Reddit's r/plantedtanks of people using yeast somehow as a Co2 source.  Could I ask someone to explain that option as well?

Absolutely yeast/sucrose (classic fermentation) was one of the first DIY CO2 systems and is by far the cheapest of them since the reactants are cheap and available at the grocery store. This was the DIY system that poor college kids could afford way back int the day. Honestly it works great, but you have to be really careful to not gas your tank with CO2 or explode the plastic bottle and spew yeast/sugar everywhere. Other than that, it has a couple of problems that make it less desirable than the citric acid/bicarbonate reactors:

• One of the byproducts of the reaction from the yeast is ethanol, which becomes toxic to the yeast at certain concentrations, so the reaction kills itself over time, usually before all of the sucrose is consumed.
• There is no real easy way to control the reaction, i.e. turn it off and on with the light cycle. Once the yeast/sugar are mixed in water, the only way the reaction stops is the alcohol kills the yeast, or the yeast run out of food and stop producing CO2.

[CT_]

On 6/30/2021 at 7:05 PM, DShelton said:

There are some great DIY systems that do just this.

I meant put acid and base IN the tank and let them react there so it starts as dissolved co2. 

[Johannes]

My local lfs has a kit which you can connect to a sodastream as that produces c02