CO2 and O2 - The Planted Tank Forum
 
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post #1 of 10 (permalink) Old 08-29-2008, 03:35 PM Thread Starter
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CO2 and O2

im confused and im lazy (what a combination )

heres straight question..

water is H20 right,with two H, and one O

- if concentration of CO2 is high so then the O2 will be low, in opposite if CO2 is low so the O2 will be high.
or,
- CO2 and O2 can be high or low concentrated at the same time, and doesnt affect each other.

wich statement is right???
and if you kind enough please explain me simply, couse im stupid
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post #2 of 10 (permalink) Old 08-29-2008, 03:45 PM
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Quote:
Originally Posted by plantoon View Post
im confused and im lazy (what a combination )

heres straight question..

water is H20 right,with two H, and one O

- if concentration of CO2 is high so then the O2 will be low, in opposite if CO2 is low so the O2 will be high.
or,
- CO2 and O2 can be high or low concentrated at the same time, and doesnt affect each other.

wich statement is right???
and if you kind enough please explain me simply, couse im stupid
You can have high or low concentrations of each depending on your setup. The oxygen and CO2 are just dissolved in the water and aren't combined or reacted with anything.

Just think of it as two flavors of powdered drink mix and a glass of water - you can have high or low concentrations of each but they both don't really affect each other.
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post #3 of 10 (permalink) Old 08-29-2008, 03:59 PM Thread Starter
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thanks mariomaster

i just saw on national geographic, theres a killer lakes, whic release its CO2 deposit

heres a silly question:

if im not get it wrong, CO2 is heavier than O2 right????

so, if i inject more O2, so the CO2 will be pushed down to lower layer(of water), and the layer upside will hold the CO2, at least give it more time, until release back to open air?????

will make CO2 injection more efficient?????
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post #4 of 10 (permalink) Old 08-29-2008, 04:09 PM
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well not sure on the relative wieght of co2 to O2 but Unless you had an absolutely stagnant tank any water movement would stir up the two gasses.
Almost everyone on here does not run any O2 into there tank due to it De-gassing the CO2. basically any bubbles will create surface movement and that allows more co2 to escape.


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post #5 of 10 (permalink) Old 08-29-2008, 05:11 PM
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Originally Posted by CrimsonKeel View Post
Almost everyone on here does not run any O2 into there tank due to it De-gassing the CO2. basically any bubbles will create surface movement and that allows more co2 to escape.
Just to clarify, surface movement increases gas exchange, be it O2 from the atmosphere or CO2 from the tank. There are also many people who use bubble wands/air stones to oxygenate the water once the lights go off.
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post #6 of 10 (permalink) Old 08-29-2008, 07:02 PM
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Quote:
Originally Posted by CrimsonKeel View Post
Almost everyone on here does not run any O2 into there tank due to it De-gassing the CO2. basically any bubbles will create surface movement and that allows more co2 to escape.
All living things need 02, I think your statement is wrong and can do
damage to someone who reads and heeds.
If you are worried about de-gassing? C02, add more C02.
The tank, plants, fish, filter media, bacteria all need 02/oxygen
on a daily basis.
Add 02 daily, preferably after adding C02.
Add C02 during light cycle.
Add 02 after light cycle until next light cycle.
Surface movement is good when it is in its perspective.

Craig

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post #7 of 10 (permalink) Old 08-29-2008, 07:40 PM
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It is true that both plants and fish need O2, but at least the fish will let you know whether or not they need more O2. Having to add O2 needlessly adds another layer of complexity to the tank. The plants will do a better job of dissolving O2 into the water than an airstone.

If the O2 generated by the plants is not enough to last the night for the fish, then you can increase the light period (could cause more algae) or just put more plants in the tank. I have never heard of fish dying because there were too many plants in a tank. If you notice your fish are distressed, then adding O2 is probably a good idea, but it should be a short term solution as opposed to long term. If you have to keep adding O2 every night to a planted tank means you are doing something wrong. Adding O2 is a band-aid and does not address the underlying problem.
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post #8 of 10 (permalink) Old 08-29-2008, 08:00 PM
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souirou... i have to disagree... plants use oxygen and release carbon dioxide at night. A heavily planted tank with lots of fish and co2 injection can indeed cause issues overnight.

the co2 injection necessary for the day cycle may be detrimental at night. Turning off the co2 at night will help, but there can be situations where co2 saturation is so high when the lights go out that there is still a detrimental affect on the inhabitants.

running an airstone at night not only relieves over saturation of co2... but also gives both the plants and fish comfortable levels of o2 to work with through the night.


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post #9 of 10 (permalink) Old 08-29-2008, 08:29 PM
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Plants produce more O2 during photosynthesis than they produce CO2 during respiration. Likewise this means they use more CO2 during photosynthesis than they use O2 during respiration. There will always be a net gain of O2 unless the plant dies and completely decomposes inside the tank, in which case there would be no gain or loss.

So for the same amount of CO2 being pumped in, more plants will only add more O2 to the tank and it will be better dissolved into water than an airstone. If somehow there is still too much CO2, then the amount of CO2 should be reduced. If you have to degas it with pumping O2, then you are wasting money on excess CO2 and pumping O2.
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post #10 of 10 (permalink) Old 08-29-2008, 09:01 PM
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I am not disagreeing with your first paragraph... although it is overly simplified. I run my tanks past the optimum co2 level. If you are running co2 at night... you are wasting it... period.

Someone with DIY doesn't have as much control over how much co2 is going into their tank at night unless they are pulling things off and/or out of their system. providing surface agitation is a very simple way of keeping the system in check.

I'm using pressurized. If I turn my co2 off at night, then co2 levels are not optimum when the lights come on in the morning. Even turning co2 on early requires me to run more co2 to catch up in time for the light cycle and also incurs an extra timer.

leaving the co2 on all the time and then running an airstone at night keeps everything evened out. I start up the morning with ample dissolved co2. And I aid my fish and my bio filters with ample o2 during the night. You may be "wasting" co2... but it's a no drama no adjustment way to ensure everyone is happy... and co2 is cheap. I don't mind spending an extra $24-$36 a year to replace co2 i may not have used if I didn't run the co2 at night.


enough with the theory... here's some real world

my 30 cube runs ph controller and also has a misting airstone on a night timer. You'd think the ph controller would keep the co2 on all night? negative. the ph controller comes on once every 45 minutes or so. That's all that's needed to keep the co2 in check.


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