Why do we start co2 an hour before light ? - The Planted Tank Forum

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post #1 of 18 (permalink) Old 12-29-2012, 03:01 PM Thread Starter
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Why do we start co2 an hour before light ?

Why do we start co2 an hour before light ?

Are you guys tricking me ? Is it because it takes that long to reach a magic 30 ppm ? Does algae benefit from the first hour when we turn light on at the same time ?

I'm sorry if this question is annoying. I just want to be informed if anyone ever asks me.
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post #2 of 18 (permalink) Old 12-29-2012, 03:12 PM
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To build up CO2 in the water before plants start to photosynthesize I believe.

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post #3 of 18 (permalink) Old 12-29-2012, 03:17 PM Thread Starter
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I guess I'm trying to understand why you would build up the c02 first. What is the thought behind that ? What would be the consequence of having both come on at the same time ?
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post #4 of 18 (permalink) Old 12-29-2012, 03:22 PM
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Different plants get started with photosynthesis at different times when the light comes on.
Some plants use a 'fast start' strategy to out-compete other plants. They can photosynthesize in the early dawn when the light level is still low. It is for these plants that we want the CO2 level to be up there pretty good as soon as the light comes on.

In nature the things that provide CO2 go on 24/7, so the effect overnight is rising CO2. The level is highest in the morning as the sun rises.
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post #5 of 18 (permalink) Old 12-29-2012, 03:25 PM Thread Starter
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Thank you Diana
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post #6 of 18 (permalink) Old 12-29-2012, 06:45 PM
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My CO2 comes on at the same time as my lights and my plants are outgrowing my tank. I just don't see that an hour makes a difference...
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post #7 of 18 (permalink) Old 12-29-2012, 07:15 PM
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Originally Posted by mjalex007 View Post
My CO2 comes on at the same time as my lights and my plants are outgrowing my tank. I just don't see that an hour makes a difference...
a lot depends on ur light level
if u have bookoos of light, ur plants need it as soon as ur nuclear blast of light comes on

on slower growing tanks, the fat reserver of carbon is used during the morning to supplement co2 dosage until proper levels can be achieved

i turn my co2 on about 30 minutes before lights, which is realyl all u should need. 45 minutes at most.. co2 concentrations change in about 15 minutes
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post #8 of 18 (permalink) Old 01-06-2013, 08:24 PM
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Should CO2 be turned off along with the lights or should it be turned off slightly before the lights go off?

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post #9 of 18 (permalink) Old 01-06-2013, 08:27 PM
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My CO2 goes off about 20 minutes before my lights do.
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post #10 of 18 (permalink) Old 01-07-2013, 01:22 AM
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Plants release co2 and consume oxygen at night when lights are off. So in the morning your water would already have a high level of co2. Turning on your co2 an hour before lights come on is just wasting co2.
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post #11 of 18 (permalink) Old 01-07-2013, 02:27 AM
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The pH of my tank at lights on without CO2 added is 7.6 and my target pH is about 6.4-6.6. I turn on the CO2 half an hour before lights go on and turn it off 40 minutes before lights go out and probably could turn it off earlier.
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post #12 of 18 (permalink) Old 01-07-2013, 05:27 AM
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Originally Posted by vqfive View Post
Plants release co2 and consume oxygen at night when lights are off. So in the morning your water would already have a high level of co2. Turning on your co2 an hour before lights come on is just wasting co2.
True and maybe as there are many other considerations that affect the co2 start timing. For example, I am running pressurized co2 in a high-light over-planted and over-populated tank. In that tank I also run a bubble wand when the co2 and the lights are off to protect the fish. When the lights come on, the concentration of co2 in the water is around the equilibrium with co2's concentration in the air, which is pretty low for plants in a high-light aquarium.

Other variables are the surface agitation, the method of the co2 injection, the co2 delivery start-up time, co2 distribution within the tank (flow), and who knows what else.

My point being that, unfortunately, one size does not always fit all.

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post #13 of 18 (permalink) Old 01-07-2013, 05:47 AM
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This whole thing with turning CO2 on and off was started by the Japanese. There are reasons that have to do with the way the plants absorb the CO2 (Diana explained it already), but also there is a concern for the biofilter, and matching the light intensity.

The biofilter does not function very well at pH values that we love to have. So at night it gets a break by not getting hit with both CO2 from the plants and from our rigged up supply.

The Japanese also time the CO2 increase and decrease with the staged light intensity that they use - the most CO2 is present when the strongest lights are on.

How much earlier you should turn on/off the CO2 is for you to find out. For example in one of my tanks it took 30 min for the CO2 to fizz out (I ran an air stone as soon as the lights went off) and 3.5 hours to build back up.

And by the way the 30 ppm CO2 is not written in stone. The 30 is suggested by EI because that approach relies on always having more than "just enough" nutrients. As many other things - the amount of a specific nutrient is specific for the method that you use and for the stage the planted tank is in at the moment. The Japanese normally maintain CO2 of 15 to 22 or so from what I can tell. Is that the max. value throughout the day I do not know.
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post #14 of 18 (permalink) Old 01-08-2013, 01:22 AM
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I have a heavily planted 150g tank with Discus lots of flow and a sump with a wet/dry filter. I set my ph controller to turn on the co2 if the water gets above 7.4. This setting keep the plants happy and fish healthy- so far. Keeps the drop checker in a nice green zone at all times.

With good O2 from the overflow box(no scum) and trickling water in the sump things have been going well. I inject the co2 by using a lime wood air stone under the sump return pump. Creates a champagne like mist in the tank. There the fluval fx5 return splits the sump return flow mist into two directions.

BUT I am considering putting the ph controller on a timer to turn off at night since Tom Barr has some very good reasons why this should be done.

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post #15 of 18 (permalink) Old 01-08-2013, 01:46 AM
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Originally Posted by dastowers View Post
I have a heavily planted 150g tank with Discus lots of flow and a sump with a wet/dry filter. I set my ph controller to turn on the co2 if the water gets above 7.4. This setting keep the plants happy and fish healthy- so far. Keeps the drop checker in a nice green zone at all times.

With good O2 from the overflow box(no scum) and trickling water in the sump things have been going well. I inject the co2 by using a lime wood air stone under the sump return pump. Creates a champagne like mist in the tank. There the fluval fx5 return splits the sump return flow mist into two directions.

BUT I am considering putting the ph controller on a timer to turn off at night since Tom Barr has some very good reasons why this should be done.
Ah good a fellow wet dryer!

With a wet/dry filter co2 cannot build up overnight. They are too efficient at gas exchange

That being said, with discus and a slightly green dc, i might consider leaving co2 on 24/7.. they are a temperamental species for sure. Ph being less important than kh and gh. But still..

That being said u are correct turning co2 off at night is advantageous, with a ph of 7.4 its not that important, ur bacteria is functioning very efficient at that level. Below 6.4 ph is when bacteria becomes mostly useless, which is the primary reason to turn off co2 at night
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