CO2 Generator Exhausted After A Few Hours

[jfcp]

I am attempting to set-up a baking soda - citric acid CO2 injector for a planted tank.

I purchased a kit from ebay (photo1) with the necessary fittings, valves, gauge, tubing, etc, and set it up, with the standard 200 ml water and 200g baking soda in bottle B (photo2), and 600ml water plus 200g citric acid in bottle A.

I made two trial runs in this way with the discharge needle valve feeding a tube to a ceramic disc diffuser immersed in about 6 inches of water.

It seems to work just fine, except for the fact that, even with a VERY low CO2 output rate to the diffuser- just enough to make a few streams of the TINIEST bubbles - the system runs down and stops, seemingly exhausted, after only about 8 hours. Shaking the baking soda bottle only renews activity of a couple of minutes, and becomes less effective with each attempt.

I am led to believe by the instructions that came with the kit that it should be able to supply a low delivery rate of CO2 for a month or more!

I checked all tubing for leaks and found none.

I should add I am using tap water, but I don't think that makes any difference.

So what's going on here?

 

[mbsqw1d]

In my experience, the valve on these kits aren't great and are very leaky. I swapped it out with a better needle valve
https://www.amazon.co.uk/dp/B01FFEN7WI/?tag=
And I also used PTFE tape on the threads on the bottles

You'd be surprised how leaky these kits can be. I was certain there were no leaks in mine but after these alterations there was an improvement

 

[StevenF]

I agree you probably have a leak You won't be able to hear or feel it because it is too small. Best way to find the leak is to either put the entire setup under water so you can see bubbles from the source of the leak or brush on a soap water mix so that soap bubbles will mark the location of the leak.

but in addition I would like to add is that the diffusers are not a very efficient way of getting CO2 into your tank.water. The most efficient way is to use the inverted bottle methode. In my small tank I was refilling a CO2 paintball tank about once every 3 months. With the inverted bottle methode I get about 1 year of use out of the bottle. So after you fix your leak replacing the diffuser with a inverted bottle will greatly reduce waste.

 

[jfcp]

In my experience, the valve on these kits aren't great and are very leaky. I swapped it out with a better needle valve
https://www.amazon.co.uk/dp/B01FFEN7WI/?tag=
And I also used PTFE tape on the threads on the bottles

You'd be surprised how leaky these kits can be. I was certain there were no leaks in mine but after these alterations there was an improvement

Ok I'll keep those ideas in mind.

Thanks

 

[jfcp]

I agree you probably have a leak You won't be able to hear or feel it because it is too small. Best way to find the leak is to either put the entire setup under water so you can see bubbles from the source of the leak or brush on a soap water mix so that soap bubbles will mark the location of the leak.

but in addition I would like to add is that the diffusers are not a very efficient way of getting CO2 into your tank.water. The most efficient way is to use the inverted bottle methode. In my small tank I was refilling a CO2 paintball tank about once every 3 months. With the inverted bottle methode I get about 1 year of use out of the bottle. So after you fix your leak replacing the diffuser with a inverted bottle will greatly reduce waste.

Hmmm.. some interesting ideas there!!

I'm a little skeptical about the problem being a leak, as 200g + 200g of reactants are used up in about 8 hours, when the kit instructions are telling me they should last a month. With easily detectable output from the diffuser, and the leak needing to be 90 times that amount (3 x 8 hrs to make a day, x 30 days to make a month), I would have thought a leak of that size would be hard to miss, but I will redouble my leak checking efforts anyway. I had been using the soap bubble method, and found NO trace of a leak anywhere.

I agree diffusers are not the best , but seemed to be the best compromise I was aware of. Your "inverted bottle" suggestion is excellent!

Are you using a "drop checker" to see what concentration of CO2 they tend to produce in a tank?

I imagine you are familiar with these, but just in case, start at time 4:40 in the video HERE:

I think control over the achieved concentration in the tank might be had by using wider or narrower bottles: wider to give a higher diffusion rate & concentration in the aquarium, narrower the reverse.....

 

[StevenF]

I imagine you are familiar with these, but just in case, start at time 4:40 in the video HERE:

Many people assume a drop checker measures the CO2 concentration in th water. It doesn't. The indicator solution in it is separated from the water by a gas bubble. Drop checker only measure the amount of CO2 outgassing from the tank. There is 400 ppm of CO2 in the air. And if you remove a drop checker from a tank It will indicate you are low on CO2. But if you put it in a container with more than 400ppm in the air it will indicate you have CO2 .

Drop checker don't work in aquariums using the inverted bottle method. But I know that there is enough CO2 in my water because I can see oxygen bubbles form under theeves of my plants. It I forget to fill the bottle I don't see oxygen bubbles forming. So to measure CO2 in a tank with the inverted bottle meted need a different methode to measure it.

unfortunately it appears to be very difficult to do unless you have DI water with nothing in it. In that case the PH of DI water can be determined CO2 levels This works because the only thing to affect the PH level is CO2.

I think control over the achieved concentration in the tank might be had by using wider or narrower bottles: wider to give a higher diffusion rate & concentration in the aquarium, narrower the reverse.....

Ihaven't tested the effect on the size of the bottle or the size of the opening. In part because it is very difficult to get determine accurately ow much CO2 is actually the water. One thing you need to understand is that CO2 bonds with water. Even if you have no plants in the aquarium and fill the bottle with CO2 it will eventually fill up with water. So if you just have a current flowing past the bottle opening to get CO2 into the water.

 

[Colin_T]

most chemical reactions occur in milliseconds so expecting bicarb and an acid to continue reacting for a month is expecting a miracle.

 

[mbsqw1d]

most chemical reactions occur in milliseconds so expecting bicarb and an acid to continue reacting for a month is expecting a miracle.

The setup has two seperate bottles, one has the bicarb solution and the other the citric acid solution. When the pressure reduces in one bottle (as it releases co2 into the tank), it draws more solution in from the other bottle which creates more reaction and more co2

 

[mbsqw1d]

By adding co2 to water you're doing co2 + h20 = h2co3 which is carbonic acid. The drop checker is measuring ph and as you are adding an acid (carbonic), then the ph will drop.

 

[Colin_T]

check the valves and connections.