Yes, constantly very low.
Possibly a dumb question about water agitation and CO2
I understand that as the photoperiod goes on, the plants use up available CO2 until it's depleted. I also understand (I think) that surface agitation balances the gases in the water. So, if I'm not adding CO2, but instead sufficiently and constantly agitating the water during the photo period, would the CO2 levels not stay relatively constant?
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1. No such thing as a stupid question
There are a ton of variables at play here. Warmer water hold less dissolved gasses, plant growth rate and density will probably play the biggest role, photo period, amount of surface agitation as gas exchange is not a very fast process (eg. drop checker takes about 2 hrs give or take to show results of dissolved gas) increasing agitation will increase exchange rate but to what extent I can't say personally. If you have relatively slow growing plants and lightly planted with lower lighting intensity or duration I would assume that this exchange would be able to keep up but at what point you would completely deplete Co2 I don't think you will find an answer. Dianna Walstad or Walstad method would be a good book to research that may help give you some estimates in this area. I can recommend some things that may help such as slow growing plants, aeration, lower intensity lighting or photoperiod (limits photosynthesis reducing consumption of C02) but this is necessary to provide growth so its a balancing act, Split photo periods would allow Co2 levels to shift back towards equilibrium increasing the Co2 again before the light come back on (Just thinking about this not fact but I would assume several shorter photo periods of say 4hrs on 2 off 4 hrs on would probably provide great benefit in this circumstance allowing Co2 to replenish in between).
Just some thoughts
Dan
There are a ton of variables at play here. Warmer water hold less dissolved gasses, plant growth rate and density will probably play the biggest role, photo period, amount of surface agitation as gas exchange is not a very fast process (eg. drop checker takes about 2 hrs give or take to show results of dissolved gas) increasing agitation will increase exchange rate but to what extent I can't say personally. If you have relatively slow growing plants and lightly planted with lower lighting intensity or duration I would assume that this exchange would be able to keep up but at what point you would completely deplete Co2 I don't think you will find an answer. Dianna Walstad or Walstad method would be a good book to research that may help give you some estimates in this area. I can recommend some things that may help such as slow growing plants, aeration, lower intensity lighting or photoperiod (limits photosynthesis reducing consumption of C02) but this is necessary to provide growth so its a balancing act, Split photo periods would allow Co2 levels to shift back towards equilibrium increasing the Co2 again before the light come back on (Just thinking about this not fact but I would assume several shorter photo periods of say 4hrs on 2 off 4 hrs on would probably provide great benefit in this circumstance allowing Co2 to replenish in between).
Just some thoughts
Dan
Borrowing from aquaculture...
That said one should mention that fish and decomposition of organic matter adds CO2 and plants can substitute carbonates if CO2 is lacking (high kH tanks have an advantage here).
So it doesn't have an easy answer..
Point of adding CO2 is to eliminate a variable to some extent..
add this to the dman's explanation..
It is not hard to envision a heavily planted tank to go to zero CO2, even w/ mixing or a largish fish load.During the day, algae take up or “fix” carbon dioxide that is free in the water
and carbon dioxide concentration is therefore lowest (often 0 mg/L) during late afternoon, when dissolved
oxygen is highest. During the night, the respiration of pond organisms produces carbon dioxide, which accumulates to a maximum
(usually around 10 to 15 mg/L) at dawn.
That said one should mention that fish and decomposition of organic matter adds CO2 and plants can substitute carbonates if CO2 is lacking (high kH tanks have an advantage here).
So it doesn't have an easy answer..
Point of adding CO2 is to eliminate a variable to some extent..
add this to the dman's explanation..
How would they stay constantly low with extra surface agitation? Doesn't that restore the 02/C02 balance (albeit maybe slowly, but still does it nonetheless)
Because the equilibrium is low to begin with... like 2-3ppm, surface agitation will only bring Co2 up to that level but not past without Co2 injection.How would they stay constantly low with extra surface agitation? Doesn't that restore the 02/C02 balance (albeit maybe slowly, but still does it nonetheless)
Dan
Me thinks me gets it.
Water agitation couldn't be enough to restore it quickly enough. At that level, it will get depleted faster than it can get restored.
Injection wins!
Merci.
Yeah, makes sense now.Because the equilibrium is low to begin with... like 2-3ppm, surface agitation will only bring Co2 up to that level but not past without Co2 injection.
Dan
Water agitation couldn't be enough to restore it quickly enough. At that level, it will get depleted faster than it can get restored.
Injection wins!
Merci.
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