# How long should I run Co2



## larusaquarium (Feb 21, 2015)

Having some BBA because of fluctuating co2 levels in my tank. My question is do you guys run co2 24/7? 
How do I find that perfect balance in my tank?
Is it safe to run 1bbs 24/7 if I have discus in my tank? I usually run co2 from 10am-4pm.


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## lee739 (Oct 12, 2014)

I run mine from 0800 until 2030. Lights are on from 1200-2100. Airstone from 2030 until 1130.
I use a pH controller and noted it takes a couple of hours to reach the pH I've set. I recently reduced light time to the 9hr, but left CO2 on time at 0800 so I can check it comes on, and the start pH before I leave for work.....

I don't think fluctuation from day to night counts. Otherwise we'd all be swarming in BBA.


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## King of Hyrule (Apr 29, 2013)

Start CO2 one hour after lights come on, and off one hour before the lights go out.


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## jrill (Nov 20, 2013)

King of Hyrule said:


> Start CO2 one hour after lights come on, and off one hour before the lights go out.


I would start it one hour before lights come on.


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## rick dale (Feb 26, 2014)

*co2*

The best way is to see how long it takes to get a 1.0 drop in ph. You will need a ph controller/monitor to accurately do this. Co2 needs to be at its targeted number BEFORE the lights come on. Keep your lights at 8 hours per day or less if you are having algae problems. Why is your co2 fluctuating ?


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## larusaquarium (Feb 21, 2015)

I don't have money for fancy ph meters and timers. So all the controls have to be manual. I'm a college student and spent the last extra money I had saved up for my tanks to buy a ro di system. So I'll be tapped out for a quite a while. Lol
Anyways starting today I will be changing up my co2 and lighting schedule. From all the replies I got my understanding is that no one can tell you exactly how to have a balance tank. I guess I have to play around a bit and find that sweet spot.


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## imcmaster (Jan 30, 2015)

larusaquarium said:


> I don't have money for fancy ph meters and timers. So all the controls have to be manual. I'm a college student and spent the last extra money I had saved up for my tanks to buy a ro di system. So I'll be tapped out for a quite a while. Lol
> Anyways starting today I will be changing up my co2 and lighting schedule. From all the replies I got my understanding is that no one can tell you exactly how to have a balance tank. I guess I have to play around a bit and find that sweet spot.


A simplistic attempt to describe balance would be as follows: The level/intensity of light you have will trigger the need for a certain level of both CO2 and nutrients. High light will stimulate a high rate of photosynthesis, thus requiring high concentrations of CO2 and ample nutrients (to build up the plant matter). At low light levels, the requirement for CO2 and nutrients is dialed back accordingly. So balance is when you supply enough CO2, and enough nutrients that the light demands. It is easier to balance when the light is lower.
The uptake of CO2 is during the photo period, so like many others do, concentrate on getting optimum CO2 levels during this time.
What is the correct CO2 level, and how do you arrive at it? It is generally accepted that growth improves when you reach CO2 concentrations of around 10ppm. Consider that if inject no CO2 the level is closer to 2-3ppm. Growth is even better as you approach higher levels in the range of 30ppm (or higher). You have a limit to how high you can go because of the toxicity to the fish, although higher levels of O2 allow you to push the Co2 level higher.
If your CO2 unit is effective at dissolving CO2, with a high enough bubble rate, you will be able to achieve your target. How do you know when you reach it? This is not easy, and I'm not sure anyone can confidently say what their CO2 level is in ppm. That said, there is an approach which will help, and it is based on the fact that the concentrations of CO2 will alter the ph level (equilibrium established based on your aquarium's buffer).
So start by measuring your pH in the morning before your lights go on (and your CO2 was off all night). You might get around 7.6. Adjust your bubble counter to 1 bps (or more aggressive if you have experience running safely at a higher rate) and let the pH settle. This may take a few hours. Measure the pH. How much did it move? Over a period of several days, slowly increase the rate each day until you get a pH drop of about .8 to 1.0 drop (continue to monitor your fish for stress). Some people keep this process going UNTIL the fish show signs.
It is at this point that you have done the best you can to stabilize CO2 at its maximum level for your tank, and should not need to adjust the nozzle any further. You can safely turn off the CO2 at lights out, and turn it back on again 1 hour prior to lights on. No need for a controller in this case. The use of a drop checker will also help determine when your CO2 levels have reached an adequate level, but I still think a pH measurement is a more disciplined approach.


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## Mathman (Apr 5, 2009)

imcmaster said:


> A simplistic attempt to describe balance would be as follows: The level/intensity of light you have will trigger the need for a certain level of both CO2 and nutrients. High light will stimulate a high rate of photosynthesis, thus requiring high concentrations of CO2 and ample nutrients (to build up the plant matter). At low light levels, the requirement for CO2 and nutrients is dialed back accordingly. So balance is when you supply enough CO2, and enough nutrients that the light demands. It is easier to balance when the light is lower.
> The uptake of CO2 is during the photo period, so like many others do, concentrate on getting optimum CO2 levels during this time.
> What is the correct CO2 level, and how do you arrive at it? It is generally accepted that growth improves when you reach CO2 concentrations of around 10ppm. Consider that if inject no CO2 the level is closer to 2-3ppm. Growth is even better as you approach higher levels in the range of 30ppm (or higher). You have a limit to how high you can go because of the toxicity to the fish, although higher levels of O2 allow you to push the Co2 level higher.
> If your CO2 unit is effective at dissolving CO2, with a high enough bubble rate, you will be able to achieve your target. How do you know when you reach it? This is not easy, and I'm not sure anyone can confidently say what their CO2 level is in ppm. That said, there is an approach which will help, and it is based on the fact that the concentrations of CO2 will alter the ph level (equilibrium established based on your aquarium's buffer).
> ...



Great explanation!


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## larusaquarium (Feb 21, 2015)

Thanks for the detailed answer imcmaster. To be honest I never had any issues when I had a low tech tank. I never did water parameter checks or had to remember to turn this off before that and turn something else on. My fish and plants did just fine. I grew my discus from 2" babies to 7"+ adults in these settings. All I did was frequent water changes (twice a week) and had 0 issues. 
Ever since I hooked up co2 plants have been growing out of control but along with that came many other side effects, such as algae. I got to say I went from 0 stress to stressed out constantly after I hooked up co2. I know getting the right balance takes time and effort. I'm going to do my best to see if I can get this balance. If I'm unsuccessful by end of April Im gonna say bye bye to co2 and go back to low tech.


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## imcmaster (Jan 30, 2015)

Very well said! I hope you achieve the balance you are looking for.

May I ask what lights you had when 'low tech'? Have you added new lights when you started with CO2?

And last about balance. Plants are happy and healthy when they get the right amount of CO2 and nutrients (for the amount of light that is driving their metabolism). If you crank up the CO2 to meet the demand, are you also dosing enough and all ferts needed (all macros and micros) to ensure that no one nutrient is non-limiting? The EI method was designed to ensure that nutrients should never be the non-limiting factor. I think your success will come when you adjust the CO2 level, and ensure proper dosing.... or in the end just lose some of the light intensity, slow the growth rate of the plants, and things will stabilize like your older low tech set up. 

Going 'high tech' requires understanding the CO2 and nutrients ...

Good luck!!


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## burr740 (Feb 19, 2014)

Some great advice above. 1 bps doesnt sound like much for a tank that's big enough to hold discus...just saying

You can get timers for 5 bucks at wal-mart or lowes, etc. You can get a PH pen from amazon in the $15 range, calibrating solution another $12-15. This will allow you to easily, and accurately measure the PH at various times of the day to see where your levels are at, and make the necessary adjustments.

I understand being a broke college student. Been there. Done that. But what's $35 bucks if it means you can better look after an already several hundred dollar investment?


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## corrupt (Jan 25, 2014)

I brought my ph pen and tds pen from e ba y for about $5 each delivered.
You dont need a ph controller just an easy quick way of testing say every 15min till you get the 1ph drop. Then keep testing through out the day (every hour??) to make sure the co2 doesnt get to high.


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## larusaquarium (Feb 21, 2015)

Awesome. I looked into the eBay ph pen a while back. I was kind of skeptical if they really work or not, so I didn't buy it. I played it safe and bought 160 ph testing litmus strips for $0.99 from [Ebay Link Removed] I will be using the strips until I save up enough to buy a decent ph controller/co2 doser. 

I'm also planning on buying some timers for my lights and co2. I got my ro di unit today and made my first batch of clean water. No more adding tds to my tank. After talking to people in this forum it's very clear that more control I have on what I add to the tank, more control I have in controlling algae growth. 
I truly appreciate all y'all's valuable advise.


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## ericwithac (Mar 19, 2015)

lee739 said:


> I run mine from 0800 until 2030. Lights are on from 1200-2100. Airstone from 2030 until 1130.
> I use a pH controller and noted it takes a couple of hours to reach the pH I've set. I recently reduced light time to the 9hr, but left CO2 on time at 0800 so I can check it comes on, and the start pH before I leave for work.....
> 
> I don't think fluctuation from day to night counts. Otherwise we'd all be swarming in BBA.


I have this same issue with my aqua fern. I can't tell if its Black Beard or Diatom. If its Diatom I hear it just takes care of itself.

In regards to the CO2/Light Cycle, Ive always been told to have the CO2 on an hour before the light come on, and turn off an hour before the light go out. 

Doing this makes my drop checker turn dark blue overnight, indicating a lack of co2. It usually takes halfway through the light/co2 cycle before the drop checker shows the light green it should be.

Should i maybe start my co2 two hours before the lights come on? Or should I switch to a 6on, 6off, 6on, 6off cycle? Would this keep the co2 levels in my tank more steady?

Thanks!


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