Weird experience with DIY CO2 - The Planted Tank Forum
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post #1 of 21 (permalink) Old 04-18-2011, 05:31 PM Thread Starter
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Weird experience with DIY CO2

Hi guys, been lurking here for a long while, finally posting because of an unexplained problem with my first try at DIY CO2.

I have set up 2X1.5L bottles for my 10g, using a mixture of 2cups sugar, 1/8 teaspoon of yeast(I'm trying to get a slower/more stable reaction). I bought the UP inline atomizer because after looking around, it seemed the most logical/minimalist/effective method of diffusing to me.

The setup goes as this:

______1.5L___________1.5L_____
_______|______________|______
___Check Valve_____Check Valve
_________\___________/_______
____3 way 2 switch manifold_____
______________|______________
Double check valve Bubble Counter
______________|______________
__Up Aqua Super inline atomizer__
______________|______________
___Ehiem ECCO Pro 200 Outlet___


It took about a day of seeing nothing before the whole system pressurized up, and after abit of swirling, the co2 bubbles started pouring out from my outlet, and within a few mins, all 10g of my tank was filled with floating tiny co2 bubbles. A little concerned about the whole tank hazing up with co2 bubbles, I disconnected it after 30 mins. Problem is, the drop checker has changed from green to yellow and stayed that way after >48hrs of disconnecting the entire yeast generator.

Worried, I decided to invest on an instant co2 checker from tetratest, and the results returned(after disconnecting the yeast generator for >48hrs) was 10mg CO2/liter of water which seem well within the limits. Now, when I tried to "activate" the yeast generator(made a new solution and connected them back for another day), it just never seem to be able to put any bubbles into the outlet.

I did alot of readup, and chanced upon a 4 yr old thread that shows the following setup to be able to obtain decent constant pressure:


I have not built gas seperator and needle valve portion of it yet, and will probably be doing so this weekend.

For the record, I have a dozen of dwarf corys, xmas moss, algae balls, rotalas and mini salvinia. In the past few weeks, only the rotala seem to have grown(triple in height actually) while the rest didnt show much growth at all. During the entire time, the corys didn't seem to do the "gasping for breathe" maneuver any more than they usually do.

Meanwhile any form of advice or comments to help improve on my system are welcomed!

Last edited by fongalv; 04-19-2011 at 12:12 AM.
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post #2 of 21 (permalink) Old 04-18-2011, 06:51 PM
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I would be concerned about adding a needle valve to a diy CO2 setup. Their is potential for building a large pressure behind the needle valve, even with a gas separator, resulting in an explosion. I understand why you want to go with two bottles, but I think that is just too much for a 10 gallon aquarium. A single bottle should be enough.

With your drop checker were you using 4 dKH solution?

Last edited by Jorge_Burrito; 04-19-2011 at 12:34 AM.
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post #3 of 21 (permalink) Old 04-18-2011, 07:08 PM
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Originally Posted by Jorge_Burrito View Post
I would be concerned about adding a needle valve to a diy CO2 setup. Their is potential for building a large pressure behind the needle valve potentially resulting in an explosion. I understand why you want to go with two bottles, but I think that is just too much for a 10 gallon aquarium. A single bottle should be enough.

With your drop checker were you using 4 dKH solution?


this is totaly WRONG unless you have a HUGE bottle, i have 5 total litres on a 5 gallon temp but it usualy has 3



if you want it to return to green raise the output of your canister for an hour or so.

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post #4 of 21 (permalink) Old 04-18-2011, 07:37 PM
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Quote:
Originally Posted by fongalv View Post
I did alot of readup, and chanced upon a 4 yr old thread that shows the following setup to be able to obtain decent constant pressure:
I recall that thread.

I'm going to cover everything except the excessive amount of CO2, since other people have already responded about that.

There is little airspace in your typical DIY CO2 system. Most of the volume of the bottles is filled with water solution, which isn't compressable. So pressure will rise quickly until something ruptures.

By providing a large airspace in the gas separator, there is a place for CO2 to accumulate, and build up pressure at a more reasonable rate.

Still, if on average the CO2 builds up faster than it is released, eventually the pressure will become excessive and something will blow. Should anything clog or a valve accidentally be left closed, this is a very real possibility. I would at very least use something larger than a 20oz. bottle for the gas separator, giving you some extra time to notice if something is wrong.

DIY CO2 does not provide pure CO2. As bubbles pop, it creates tiny droplets of water, containing yeast, sugar, and alcohol; which are light enough to get carried through the lines. The CO2 also mixes with the water to form carbonic acid. And who knows what else is being produced as a result of fermentation.

All these impurities can attack and clog both the delicate needle valve and fine pores of the inline diffuser; or provide nutrients for bacteria/algae growth which will clog them. A gas separator will help reduce that, but probably not eliminate it entirely. You may have clogged your inline diffuser already, which is why you can't restart your system; although you should rule out other possibilities, like leaks.

This is why I don't use valves (other than check), or any diffuser element with fine pores that may clog, with DIY CO2. No back pressure at all means little can go wrong. Not to say it can't be done, but as you're finding out, it's tricky.

Unless you're using some specialized yeast (rather than common baker's yeast), 2 cups of sugar is excessive. The alcohol will kill the yeast long before it uses all the sugar. 1.25 cups is probably closer to optimal. You can taste the mixture when fermentation ceases (or drops below useful) to see how much sugar is left, and see if it needs to be adjusted.

Finally, drop checkers often take a while to respond; and longer to respond to a drop in CO2 than an increase. Sometimes after being exposed to an excess of CO2 (especially if CO2 bubbles rise into the checker), they seem to take forever to return to an appropriate color; if at all. At that point, I just empty them out and refill with new indicator solution.
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post #5 of 21 (permalink) Old 04-18-2011, 09:48 PM
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Quote:
Originally Posted by JamesHockey View Post
this is totaly WRONG unless you have a HUGE bottle, i have 5 total litres on a 5 gallon temp but it usualy has 3



if you want it to return to green raise the output of your canister for an hour or so.
Our experiences differ then. I had a standard 2 liter diy setup on a 5 gallon and it would bring a drop checker to yellow for the first two weeks. I ended up having to go to a different method of CO2 delivery because of this. Diffusion methods, tank agitation, and plant load all can contribute to differences. The fact that the OPs drop checker went yellow suggest he has too much CO2 and needs to eliminate a bottle.
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post #6 of 21 (permalink) Old 04-19-2011, 12:43 AM
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I know this much. When using champagne yeast, I nearly killed every fish in my tank by using a 1-gallon yeast reaction jug (3.78 liters).

This was a mix using the champagne yeast, sugar, baking soda, and some ammonium phosphate. Overnight it overloaded my XP3 Filstar, which I had to re-prime. During the day, when it hit it's maximum production, I had lost a number of fish, mostly cardinal tetras and otos.


I wouldn't personally be willing to put a needle valve on my DIY CO2 setup unless I had a container that I trusted more than a soda bottle. Then, it would probably be just fine.


Anyone have any idea what that much pressure would do to yeast and CO2 production?
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post #7 of 21 (permalink) Old 04-19-2011, 02:03 AM Thread Starter
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Hi guys, thanks for all the input. I guess I need to reiterate that my co2 check seems to be well within limits at 10mg/light using the tetratest co2 measurement vials.

I am purely stocking dwarf corys now, and I am inclined to believe that they are biologically tuned for a low oxygen environment since they have a natural tendancy to do the 'rush for air' maneuver which they have not been performing more then they usually do compared to before injecting co2.

As for the co2 mixture, after all the research I was under the impression that the speed of reaction depends on the amount of yeast and not sugar? Can someone kindly explain why went more sugar will produce more alcohol if the rate of production stays the same?

To be on the safe side, I have placed a fan across the surface to create some movement so excessive co2 can be lost through the agitation, for now...

The drop checker is still yellow and I'm already at full filtration rate(my filter is overspec'ed for my tank size), and gonna move the drop checker to the front of the tank when I get back... its been yellow for almost 60 hours with no co2... photo period at 12 hrs daily.
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post #8 of 21 (permalink) Old 04-19-2011, 03:10 AM
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I use 1 liter for my 29 gallon. Even with a 1 liter, you can still kill your fish to death.

I also use a needle valve and close it up at night. what can i say; i like risk.

My feelings: The caps will fail before the bottle will rupture (~200psi). The silicone glue used where you connect the hoses to the caps will fail before the caps will fail.


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post #9 of 21 (permalink) Old 04-19-2011, 03:19 AM
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Quote:
Originally Posted by esworp View Post
I use 1 liter for my 29 gallon. Even with a 1 liter, you can still kill your fish to death.

I also use a needle valve and close it up at night. what can i say; i like risk.

My feelings: The caps will fail before the bottle will rupture (~200psi). The silicone glue used where you connect the hoses to the caps will fail before the caps will fail.
This is a good point, but constantly having to redo connections is no fun either.

OP: I would replace your drop checker solution and see if you still get a yellow reading. Sometimes the solution just seems to get messed up and needs replacing. I know not very technical explanation, but I have experienced it a couple times where it goes yellow and stay that way, even if brought out of the tank.
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post #10 of 21 (permalink) Old 04-19-2011, 07:47 AM
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Fongalv, this just got posted. Check it out:

https://www.plantedtank.net/forums/di...regulator.html
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post #11 of 21 (permalink) Old 04-19-2011, 10:29 AM Thread Starter
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Thanks Darkcobra, saw that thread, quite interesting!

I anticipated the cap/hose connection to be the weakest link, hence I gave it extra attention and actually put the check valve inside the cap. I did this because having a higher pressure on the generation side means the check valve will always be pushed against the cap, then hot glued both sides just in case...



The co2 tubing at the bottom was to reduce the amount of liquids entering the valve.
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post #12 of 21 (permalink) Old 04-19-2011, 06:15 PM Thread Starter
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I've just got home and gave it a check, drop checker was still yellow...gave up so I did a 50% WC and replaced the dropper liquid and also moved the drop checker to the front of the tank where its probably a little more ventilated. Will check back in a couple hours time, sort of left the DIY co2 running since its running like 1bpm(if not even less) now, and the corys seem perfectly fine, lights have been switched off because I want to see if the system really overloads with co2 in the worst case scenario....

Theres still no visible co2 bubble, BUT what I noticed when I gave both 1.5L bottles a swirl was a very faint mist/vapour coming out from the outlet. Its not tiny bubbles, but an extremely fine mist, almost like slightly cloudy water. This is in line with what I have seen people using the same inline atomizer get, albeit at a much less intense rate which I'm actually quite happy about for now. I guess the tiny bubbles "7-up' effect was just a freak accident since I couldn't recreate it again?

Next challange would be to build up the gas separator and achieve a more stable pressurised system. Sometimes its 1bpm, but when I move the bottles a little, a stream of bubbles pass the counter. I suspect its the rather long run of stretchy silicone tubing between the manifold and bubble counter thats the problem. Will swap them for the remaining rigid co2 tubing once I have more time to re-assemble the CO2 system!
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post #13 of 21 (permalink) Old 04-19-2011, 06:57 PM
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Maybe the original bubbles you saw were insoluble air being purged from the system. If you've left your system of check valves intact since then, there's less air this time. CO2 can fully dissolve before reaching the outlet.
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post #14 of 21 (permalink) Old 04-20-2011, 03:04 AM Thread Starter
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Thanks darkcobra, and that does make sense since the new system will be filled/pressurized with the air inside the house devices first. Probably why the bubbles collected as a surface layer as well... should have taken a photo!

Anyway the good news is that the new drop checker liquid changed from blue to green overnight withoutlights on (its morning over here now), I suppose I should be able to leave the co2 on all the time then?
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post #15 of 21 (permalink) Old 04-20-2011, 08:43 AM
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Anyway the good news is that the new drop checker liquid changed from blue to green overnight withoutlights on (its morning over here now), I suppose I should be able to leave the co2 on all the time then?
Sounds promising. Keep an eye on it for a while.
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