# Co2 and lights on same timer?



## Mr.Yuk (Jul 30, 2014)

If you run a 6 or 8 hour photo period, perhaps split up as 2 hours in AM and 4 hours in PM, does it make sense to run the pressurized co2 solenoid off the same timer as the lights? rather than running it 24/7, or running it on some other schedule?
thanks


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## SprManKalEl (Mar 12, 2013)

I am no expert as I am still learning myself. However, I think you want your photo period to be one shot. I used to split it up but was advised against that on the thought that your fish and plants need a day similar to ours. A period of light and a period of dark instead of light-dark-light-dark. I do DIY CO2 which doesn't produce enough to have to be turned off. However, I am sure that you should turn your CO2 on about 2 hours before lights.


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## Raymond S. (Dec 29, 2012)

Not speaking from experience. I don't use CO2 except for Excel, that CO2 substitute.
I have read on here many times that with an injected system you should start 1-2 hrs
before the light comes on(depending on who wrote it) and then off an hr before the lights go off. Some also say 1/2 hr before.
They do now have multi function timers. If yours is not one of them, it would seem
better to use seperate timers.
Please wait for other replies as without experience, my credibility in this matter is at least questionable. Just letting you know what I have read on here.


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## greaser84 (Feb 2, 2014)

Most people myself included run the C02 about 1 hour before the light come on, you want the C02 to build so when the lights turn on the plants can start using C02 immediately.


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## Aquadawg (Aug 18, 2012)

I use three timers. One for co2, one for t5 white and red, and one for T 5 and blue. 10:30- 8:00 is Co2, 12:00 - 8:00 t5 and blue, 1:00- 9:00 t5- and red. Its a personal choice. Key here is co2 on before lights are and off before lights are off with only one photo period. 90- 120 minutes seems like a good rule of thumb to me. And if you ask me why the one photo period I can only say, "because I said so" LOL


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## treben (Jun 26, 2013)

This is the reason that you should have your co2 on a separate timer from the lights. Some people have BBA issues if their co2 isn't allowed to build up before the light comes on. 



greaser84 said:


> Most people myself included run the C02 about 1 hour before the light come on, you want the C02 to build so when the lights turn on the plants can start using C02 immediately.


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## RainSong (Jun 30, 2011)

I use the same timer for both the lights and the CO2 (pressurized). I understand and appreciate starting and stopping the CO2 a little before the lights, however, I have decided to go with just 1 timer. I do this for a couple of reasons:

1. Simplicity. I still find myself changing my photoperiods and having to mess with only 1 timer is easier.

2. Safety. Timers can and do fail. Also, we do have power failures from time to time. My biggest fear is the CO2 running when the lights are off for a long period. Keeping both on the same timer makes this virtually impossible. If the timer fails, it fails for both the light and CO2. If you have separate timers, there is a distinct possibility of 1 timer failing. This could result in a bad situation for your fish.

I am going on a 2 week vacation soon ... and feel a whole lot better having both on the same timer during this time.


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## talontsiawd (Oct 19, 2008)

I have done split photo periods a lot. I usually split up the CO2, though I do have it come on an hour before the lights come on. I recently switch back to a conventional photo period but I was running my CO2 through the siesta. The reason for that is it tended to off gas a bit too much so I added some time and it got to where the amount of time off was only about 1 hour. Plus, I was adjusting my CO2 which with only 4 hours on at any given time, it was hard to find the sweet spot.

Some will say that it's better to run your CO2 through the siesta (off) period as it gives more time for your CO2 to build and increases consistency when the lights are on. When I was running HOB's, I likely would have agreed as it can off gas the CO2 really quickly but with a canister, I think an hour of "lead time" with the CO2 is fine.


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## Steve002 (Feb 7, 2014)

I've read other posters say that the period required by the plants to get up to full speed on photosynthesis is 2 or more hours so that would suggest splitting the light period may not be very efficient from a growth point of view (hence leading to algae problems etc). No personal experience on this though.


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## RANDY2 (Oct 30, 2017)

please help,
when using a pressurizing CO2 system how many bubbles per second should you set it ?
should lights come on when CO2 starts or one hour before ?
any help will be appreciated
Randy


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## Darkblade48 (Jan 4, 2008)

RANDY2 said:


> please help,
> when using a pressurizing CO2 system how many bubbles per second should you set it ?
> should lights come on when CO2 starts or one hour before ?
> any help will be appreciated
> Randy


Bubbles per second is only a (very) rough estimate of how much CO2 is being injected. How much is being dissolved into the water, along with your plant load will determine how much CO2 is required.

Most people like to have the CO2 come on one hour before the lights, and then turn off one hour before the lights.


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## houseofcards (Mar 21, 2009)

Generally speaking lights on, co2 on. lights off, co2 off. As mentioned some like to start the co2 an hour or so before the lights. Every tank has different demands and needs to get plants to grow and prevent algae. I usually just have my co2 and lights on the same timer. 

I don't see this as a big issue either way. Most who have hi-tech tank with co2 are doing regular water changes and their co2 levels will go down during the change, unless there only doing the water changes at night when the co2 is off, which is unlikely.


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## mikluha (Dec 4, 2015)

I turn CO2 on/off using photosensor, which "looks" at lights. More reliable than timer. For example, during weekends I may override timer and run lights all day long.
Did it myself using arduino.

As extra precaution against too much CO2 during night time (pH drop) the extra water agitation is turned on when lights are off.


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## Kayak83 (Apr 18, 2017)

mikluha said:


> I turn CO2 on/off using photosensor, which "looks" at lights. More reliable than timer. For example, during weekends I may override timer and run lights all day long.
> Did it myself using arduino.
> 
> As extra precaution against too much CO2 during night time (pH drop) the extra water agitation is turned on when lights are off.


I was just wondering what I could do with the Raspberry Pi and my aquarium. Or Smartthings.


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## sudeep (Jun 25, 2017)

I just put my ph controller on a timer. I.E not the ph controller itself , what i mean is the solenoid is on a timer which is connected to the ph controller. So at the prescribed time that is 1 hour before lights for me the timer goes on, and the ph controller supplies power to the solenoid to being the ph down and keep it there till lights off at which time the timer kicks in and switches off the solenoid. i did not want to put the controller on timer as i have read previous reports of it loosing all memory on repeated on and off cycles and also loosing calibration. this way the ph controller is always on.


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## Kubla (Jan 5, 2014)

Having the CO2 on an hour before lights go on and off is a general guideline that usually works well. CO2 is only needed with lights on but you turn it on early so it can get to it's maximum level before the lights start (CO2 changes/flucuations with lights on are not good). You can turn it off early because it takes a while to drop. No since wasting it.

Don't know if it's valid or an internet/forum myth, but what I've always seen as the whole idea behind the split photo period is that plants can adapt to it quite easily but algae can not.


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## paulbert (Jan 22, 2017)

Here's a graph showing the ph drop over time with CO2 injection. I was starting the CO2 two hours before the lights turned on. You can see how the ph stays low even after the CO2 is turned off.


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## Tinatinm (Oct 15, 2021)

Raymond S. said:


> Not speaking from experience. I don't use CO2 except for Excel, that CO2 substitute. I have read on here many times that with an injected system you should start 1-2 hrs before the light comes on(depending on who wrote it) and then off an hr before the lights go off. Some also say 1/2 hr before. They do now have multi function timers. If yours is not one of them, it would seem better to use seperate timers. Please wait for other replies as without experience, my credibility in this matter is at least questionable. Just letting you know what I have read on here.


 Excel is not substitude of CO2!


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