# CO2 stability



## beeky (25 Oct 2007)

Rather like Matt, I had an epiphany moment this morning, although mine was when I was driving to work....

I'd been thinking about getting some CO2 in my tank as it seems all the rage at the moment, and was wondering about DIY/yeast/FE's etc. The general consensus seems to be that you need stable CO2 and to achieve this, you should do away with pH controllers/solenoids and inject 24/7. But then, I thought, the CO2 concentration would go up at night as the plants wouldn't be using it and then it would come down in the morning when the lights were on. That doesn't sound very stable. But pH controllers effectively do provide a stable CO2 as the pH is related to CO2 concentration.

Discuss!!


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## Matt Holbrook-Bull (25 Oct 2007)

that would be true if nothing else in the tank effected PH, which unfortunately isnt the cast.. hardscapes, substrates and even planting all effect the PH to some extent.. this is why PH controllers cant be relied upon to maintain stable co2, and also why a drop checker is the only way to accurately measure CO2, because no outside factors can influence the fluid inside the drop checker.


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## Ed Seeley (25 Oct 2007)

pH is also linked to an awful lot of other things to.

pH will drop if acids are added, e.g from peat or bogwood, and from the activity of bacteria in the filter among a number of other things.  So a pH meter connected to CO2 will actually probably give you less stable pH levels as it is 'constantly' tweaking the CO2 to regulate pH.  IMHO, better to set a stable bubble rate, measured by a drop checker too, and keep it running from about an hour before lights on to lights off.  But then others are finding constant CO2 works really well too; I just have pretty high stocking levels and am using disposable CO2 so don't want to pump CO2 in while the plants aren't using it!

DIY CO2 production will depend on the temperature of the vessel, amount of Yeast, amount of sugar, age of the culture and lots of other things too I'm sure so that's not really very dependable either, but better than nothing!

What we really need for stable CO2 levels is a pH meter linked up to a drop checker of known KH which can then be set to keep CO2 at 30ppm for example as the only factor that would change the pH of the drop checker would be the concentration of CO2.


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## Dave Spencer (25 Oct 2007)

The CO2 in my tank may not be 30ppm exactly throughout the photooperiod, and it will gas out during the lights off period, but I have interpreted stable CO2 as levels following roughly the same pattern every day. With this repetitive pattern, plants are able to adapt to it and maximise carbon uptake.

And, of course, a CO2 dropper is considerably cheaper and lower maintenance. I love my gadgets (got a Nikon SB-600 flash gun through the post this morning,  ), but the pH controller just seems like a gadget too far for me.

Dave.


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## Matt Holbrook-Bull (25 Oct 2007)

me too Dave...

Eds, ive often wondered to the feasibility of making a drop checker to house a PH probe.. the trouble is with that, is that the amount of liquid youd need for it to work properly, would produce such a lag in the time it takes for any changes to be measured, that it would render it useless.. not to mention pretty dangerous


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## Ed Seeley (25 Oct 2007)

Dead right Matt.  The same fact hit me as I was driving to see my Gran in hospital not long after posting that.  Maybe the answer might be some kind of gaseous probe that would work quicker enclosed in an open bubble or inside a permeable membrane?  After all you can get  gas detectors for Carbon Monoxide.


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## Matt Holbrook-Bull (25 Oct 2007)

eds said:
			
		

> Dead right Matt.  The same fact hit me as I was driving to see my Gran in hospital not long after posting that.  Maybe the answer might be some kind of gaseous probe that would work quicker enclosed in an open bubble or inside a permeable membrane?  After all you can get  gas detectors for Carbon Monoxide.



you can yes  but theyre Â£1000's.  For the purposes of the hobby, I think were a bit stuck with what we got *sigh*


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## Hoejay (29 Oct 2007)

I'm fairly new to the planted aquarium so took advice from George on th PFK forum to change from  a  DIY yeast set up ( 2 coke bottles)  to a "low tech"  :!: FE based pressurised system as described on this forum. Running a rhinox 5000 diffuser under the External filter outlet to create a Co2 mist.

I run the CO2 24/7 controlled only by the by the needle valve a bubble counter and a drop checker using 4dkH solution with bromo blue indicator. it takes about an hour to stabilise back to normal.  I only realy notice significant changes in indicator colour when I remove and replace the drop checker after water changes. I would estimate the CO2 to be around 20ppm.

My current set up is a bit between low and high tech. In terms of light about its 1.2wpg (4x30w fluoresent as standard) and  I use a modified EI dosing regime approx 40-50% water change weekly with a once weekly dosing of macros I dose 1/4 tsp KNO3 and 1/32 tsp K2PO4 and a trace liquid fert after the water change. ( 4 parts RO to 1 tap) Substrate is probably not as good as it could of been but overall I  am fairly happy with the plant growth. (There are some plants that do not seem to fair so well.) I have assumed this is mainly due to light possibly temp 28 degree C., but may be due to low EI dosing) At some stage I will upgrade the lighting.

Comment & advice most welcome


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## Matt Holbrook-Bull (29 Oct 2007)

Hoejay, you might want to try splitting your dosing over 2 or 3 times a week.. plants prefer little and often rather than large weekly meals  may perk them up a bit and get them used to your schedule a bit more effectively.

also, if your using RO for the benefits of your fish then cool... but if your using RO for the plants, it wont benefit them at all, infact, theyd be better off in tap water as it has more minerals in it.


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