# pH controlled CO2 off at night??



## Yo-han (Oct 15, 2010)

I've read something interesting about CO2 last night and I was hoping someone could help me out.

I read that a constant CO2-value of about 25-30ppm is not good for the bacteria in you filter. They'll suffer from hypoxia and will die, leaving an oil film at the surface. I do, like many people, use pH-controlled CO2, adding less CO2 at night when plants don't grow, but leaving the amount of CO2 the same 24 hours. I want to keep the pH-controlled CO2 for a more accurate CO2 amount then by adjusting it according to drop-checkers. Off course, I can adjust my pH value every night and morning by hand, but I want this system to run when I'm gone as well.

My idea is to use a timer to turn the CO2 off when light go off and turn it on 1 or 2 hours before lights go on. And if this is not enough I can even turn on an oxygenpump at night. Has anyone ever tried this before? Or does anyone know whether it is a problem to turn a pH-controller on and off (regarding calibration or anything)

Any information is welcome!

Regards,
Johan


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## ray-the-pilot (May 14, 2008)

Yo-han said:


> I've read something interesting about CO2 last night and I was hoping someone could help me out.
> 
> I read that a constant CO2-value of about 25-30ppm is not good for the bacteria in you filter. They'll suffer from hypoxia and will die, leaving an oil film at the surface. I do, like many people, use pH-controlled CO2, adding less CO2 at night when plants don't grow, but leaving the amount of CO2 the same 24 hours. I want to keep the pH-controlled CO2 for a more accurate CO2 amount then by adjusting it according to drop-checkers. Off course, I can adjust my pH value every night and morning by hand, but I want this system to run when I'm gone as well.
> 
> ...


There is a lot of opinion and theory on the internet but often not much fact. I have a CO2 controller and I never change the level of CO2 in my tank. I keep it at the lowest level necessary for my plants. This is a blue green color on my drop checker. I've been doing this for over two years. Both my plants and fish have thrived. The following fish species have bred under these conditions. Neon Tetras, Oto Cats, Angel fish. 
These are facts not opinion.
Now my opinion is that a low level of CO2 is not harmful to most species of fish even if on 24/7.


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## Yo-han (Oct 15, 2010)

I totally agree with you on the fact that 'low' levels (I specify this to <30ppm if I may) of CO2 are not harmful to most species of fish even for 24/7. But what about bacteria? In particular aerobic bacteria in the substrate and your filter. The oxygen-level in the filter and substrate is relative low when the number of bacteria is high and CO2 is above 15 ppm. Will these bacteria proliferate better if CO2 is off at night? And can you just shut off the power of a pH-controller?


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## ckarr (Nov 20, 2010)

Why not get another solenoid (attached to a timer) to cut CO2 off before it gets to the controller?


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## mrakhnyansky (Nov 25, 2007)

Yo-han said:


> I totally agree with you on the fact that 'low' levels (I specify this to <30ppm if I may) of CO2 are not harmful to most species of fish even for 24/7. But what about bacteria? In particular aerobic bacteria in the substrate and your filter. The oxygen-level in the filter and substrate is relative low when the number of bacteria is high and CO2 is above 15 ppm. Will these bacteria proliferate better if CO2 is off at night? And can you just shut off the power of a pH-controller?


I have CO2 controller on the timer with solenoid, it does require calibration around every 1-2 months.I don't like to inject CO2 during the night. It is good idea to use air stone at night, bacteria needs it. Instead of air stone you can increase the circulation during the night time by adding a pump that is on the timer. Increase in circulation or addition of air stone helps bacteria in the filter. Also you need to understand the fact that increase in CO2 does not mean decrease in oxygen. However when you aerate the tank at night, by morning none of CO2 remain in the water by the time lights on. You will end up with fluctuating levels of CO2. This may cause algae. You need to lit your tank gradually( not all light bulbs at once).Addition of recommended dose of Seachem Excel or Glutaraldehyde (Cidex) in the morning hours would help.


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## Yo-han (Oct 15, 2010)

mrakhnyansky said:


> However when you aerate the tank at night, by morning none of CO2 remain in the water by the time lights on. You will end up with fluctuating levels of CO2. This may cause algae. You need to lit your tank gradually( not all light bulbs at once).Addition of recommended dose of Seachem Excel or Glutaraldehyde (Cidex) in the morning hours would help.


I always assumed that fluctuating CO2 levels only causes algae when the levels fluctuates during plant growth (light on). So as long as I turn the CO2 on early enough, the CO2 levels are at 30ppm before lights go on and it doesn't have influence on algae growth.

And you are saying that as long as I calibrate the electrode a little more often, it won't be a problem.

Regards


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## spdskr (Apr 24, 2006)

Yo-han said:


> .....The oxygen-level in the filter and substrate is relative low when the number of bacteria is high and CO2 is above 15 ppm....


Isn't this confounded by flow rates, substrate types, dissolved O2 levels?

I use a pH controller for my CO2 system. I keep the CO2 at a level just below what causes my fish to gasp and my shrimp to show stress behavior. I do not shut off CO2 at night. The stem plants in my heavily planted tank pearl for at least half of the light period, indicating O2 saturation. My high tech tank has been operated in this fashion for 5 years.

My point is, unless your tank is already showing the signs of bacteria stress you refer to, perhaps the extra caution and equipment is not needed.


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## ray-the-pilot (May 14, 2008)

Yo-han said:


> I totally agree with you on the fact that 'low' levels (I specify this to <30ppm if I may) of CO2 are not harmful to most species of fish even for 24/7. But what about bacteria? In particular aerobic bacteria in the substrate and your filter. The oxygen-level in the filter and substrate is relative low when the number of bacteria is high and CO2 is above 15 ppm. Will these bacteria proliferate better if CO2 is off at night? And can you just shut off the power of a pH-controller?


While the idea that CO2 is harmful for aerobic bacteria is also an interesting theory, it is not supported by the fact that my tank and many others run CO2 24/7 without any problems with ammonia or nitites. The fact that I have numerous fish spawn would indicate that the water quality is good.

After 2 1/2 years I've found that my biggest problem is excessive plant growth. You will need to trim most plants at least once a week or your tank will become a jungle.

If you absolutely must turn youe CO2 off, I would not turn off the controller. I would turn off the solenoid valve that opens and closes when CO2 is called for.

BTW, I only calibrate my controller when I replace the probe. As long as the pH reading is stable and your drop checker is dark green, you are in control.


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## Andy Ritter (Nov 26, 2008)

ray-the-pilot said:


> While the idea that CO2 is harmful for aerobic bacteria is also an interesting theory, it is not supported by the fact that my tank and many others run CO2 24/7 without any problems with ammonia or nitites. The fact that I have numerous fish spawn would indicate that the water quality is good.
> 
> After 2 1/2 years I've found that my biggest problem is excessive plant growth. You will need to trim most plants at least once a week or your tank will become a jungle.
> 
> ...


I 100% agree. I've always had my CO2 going 24/7, back when I didn't use a solenoid and simply counted bubbles, and now with a controller. I have never seen a fish, shrimp, or any other creature "gasping" at the surface, although I don't doubt that elevated CO2 levels could cause it. I've even checked out my tank in the middle of the night (simply because I was up and was curious what the guys do at night) and first thing in the morning, and they have always seemed fine. I even have my drop checkers more toward a light green color. My plants pearl with oxygen bubbles beginning around mid-day, so I feel that I'm getting good CO2 levels, especially since I don't use really high level lighting. I figure that since the oxygen is supersaturated during the day, that even though my tank is VERY heavily planted, and I have a pretty high fish/shrimp load, the oxygen level is still plenty high to support them throughout the night.

But, if you still want to turn off your solenoid at night, I would recommend a really easy way to do it. Just plug a short extension cord into the output receptacle on the controller (where the solenoid is plugged in now), then plug a simple lamp timer into the extension cord, and then plug your solenoid into the timer. Set the timer for whatever time you want to allow the solenoid to function, and it won't matter if the controller is trying to turn it on at night.

As far as the calibration of the controller goes, the biggest thing that you need to be worried about is whether the probe is responding quickly enough. You could actually calibrate the probe to an incorrect pH reading, and still have proper CO2 levels as long as you had the on and off set points also set to an equally incorrect pH reading. As long as you have a properly set-up drop checker, you just need to keep adding more CO2 until the drop checker is green. The actual pH figure is irrelevant.

Just my two cents.

Andy


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## ray-the-pilot (May 14, 2008)

Yo-han said:


> I totally agree with you on the fact that 'low' levels (I specify this to <30ppm if I may) of CO2 are not harmful to most species of fish even for 24/7. But what about bacteria? In particular aerobic bacteria in the substrate and your filter. The oxygen-level in the filter and substrate is relative low when the number of bacteria is high and CO2 is above 15 ppm. Will these bacteria proliferate better if CO2 is off at night? And can you just shut off the power of a pH-controller?


OK again this is a theory but what are the facts?

My controller has been on 24/7 for over 2 years. I don't have any NH3 or NO2 problems so I guess my bacteria are doing fine. In doing this plant thing for over two years here are the problem that I faced in order of severity:

Excessive plant growth
Plant eating fish
Algae

Do you notice that I have never had any problem with fish health?

BTW You do realize that plants do what bacteria do but better?


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## Yo-han (Oct 15, 2010)

ray-the-pilot said:


> OK again this is a theory but what are the facts?
> 
> My controller has been on 24/7 for over 2 years. I don't have any NH3 or NO2 problems so I guess my bacteria are doing fine. In doing this plant thing for over two years here are the problem that I faced in order of severity:
> 
> ...


I don't have facts, I was hoping to get them here I never had problems with my fish either. I do have some algae issues sometimes (overfeeding my angelfish) and my angelfish ate all of my blyxa japonica. I just found it an interesting though and was wondering whether someone else experimented with this. But I do like this though as well:


ray-the-pilot said:


> BTW You do realize that plants do what bacteria do but better?


 Although I must make one remark, plants do absorb NH3 and NO3 quite good but NO2 rather pore. Without bacteria converting NO2 to NO3 your fish will not do as good as you say they do.

So my idea was to keep the bacteria happy as well and I started questioning whether they were without extra oxygen during the night after reading the article. (I noticed this sounds like they are my best friends, but you see my point)

So I think I will keep injecting 24/7, unless I have problems regarding NH3 or NO2. Thank for the input everyone!!


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