# Define "Fluctuating co2 levels"



## josolanes (Feb 28, 2012)

When I read about fluctuating co2, I think of a non-regulated co2 setup where the co2 levels will vary constantly throughout the day with temperature fluctuation. So there may be too little at one hour and the next may have too much, etc, etc non-stop.

You do bring up an interesting point with water changes, though. But maybe that's not frequent enough of a change to really be any concern - as you said, you haven't had any algae issues


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## The Trigger (May 9, 2012)

Yeah he's right it more has to do with changes throughout the day. Most people know yeast speeds up in warmer temps and slows down in cooler temps. So if you have a DIY reactor than early in the morning you could have 10ppms of co2, noon you could have 20, than evening your back down to 10. My area the temps vary greatly in the spring and fall throughout the day so DIY caused me nothing but problems. It would just bounce around all day in the rooms temp swings.


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## Hoppy (Dec 24, 2005)

Actually, most tap water contains a lot of CO2, so after water changes you have more CO2 than before the change, unless you are using pressurized CO2 or a good DIY CO2 system. Fluctuating CO2, in my opinion, means that you don't have about the same concentration of CO2 every day. Plants adapt to whatever level of CO2 you have. So, if they are adapted to growing with 30 ppm of CO2 and the level drops to 10 ppm for a few days, the plants have to switch to a different mode of growth, which slows or stops their growth for awhile. That gives algae an opportunity to start growing.

When the CO2 starts each day at a low concentration, then builds up to high concentration during the first hour or so after the lights come on, that isn't fluctuating CO2, in my opinion. But I notice that Plantbrain now uses dimmable T5 lighting, and lets the light intensity start low and build up as the CO2 concentration also builds up. This may be the best way to avoid even any effect of the daily variation in CO2 concentration.

If temperature variation is giving you a variable DIY CO2 output you can fix that by keeping the CO2 generators in a bath of water, with an aquarium water heater in the bath, so the water temperature stays constant.


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## 150EH (Dec 6, 2004)

My idea of fluctuating CO2 would be a system that is set daily by trying to achieve the same bubble rate with no solenoid to keep a set rate of flow daily or a low tech tank with weekly water changes where you upset the balance by giving the plants a small amount of CO2 one day a week (or 2) when the tank would be better with changes every other month, thus causing you own algae problems. As for yeast or DIY, I would consider that not to be constant but the changes may be slow enough not to have a negative effect on the system, but I've never tried yeast.

I can say water changes do lesson the amount of CO2 in my tank so I try to do them early before it comes on but it's so brief I don't think it matters much and just one of my dysfunctions.

I also agree with the natural build of light with a mid day burst, in most areas the sun is strongest for a bout 3 hours a day, this also lets CO2 build. I'm also a fan of lights out for 30 minutes after mid day just as you would have a tropical thunderstorm after the heat of the day, this has worked very well for me.


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## mindfestival (Jul 23, 2011)

150EH said:


> . I'm also a fan of lights out for 30 minutes after mid day just as you would have a tropical thunderstorm after the heat of the day, this has worked very well for me.


Maybe worthy of a new thread, intermittent photoperiods.

Is there evidence to suggest that this has an effect on the plants apart from briefly stopping photosynthesis?

Perhaps it is more for the creatures.


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