# Another CO2 question (pH controllers do not apply).



## Manwithnofish (Mar 12, 2008)

I'm fighting algae issue trying to get my CO2 / ferts off the ground and get things in balance. Several people made statements on the subject of irregular or inconsistent amounts of CO2 causing problems.

It seems a lot of people turn their CO2 off at night to correspond with the demand. Recently, someone suggested that I let the CO2 run 24/7. Just wondering what the general opinion is on this?


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## Complexity (Aug 11, 2008)

The general concern with leaving the CO2 turned on at night is that it could build up to toxic levels for the fish.

When the CO2 is on during the day, the plants use it and release oxygen. So the amount of CO2 being dosed is reduced by the plants.

However, at night, the plants no longer photosynthesize so they do not use the CO2. Continuous dosing of CO2 can cause it to build up to a higher concentration than the fish can tolerate. The CO2 will reduce the oxygen in the tank which will cause the fish to gasp at the surface.

This is why I like to use a pH controller so when the plants are no longer using the CO2 at night, the pH controller will reduce the amount of CO2 being dosed.

BUT, since it appears that you do not want to get a pH controller, you could either plug the regulator into the timer for the lights OR let it run 24/7 and do something to increase the oxygen levels at night (airstone or surface agitation).


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## houseofcards (Feb 16, 2005)

Running co2 at night won't accomplish much. The plants aren't doing much with it at night. The reason algae doesn't grow is because the plants are growing well and there is little organic content available to be utilized by algae. Now in a new setup or in a thinly planted tank you need to have very good control over your lights and have a strong bio-filter to take up the space that a new or thinly planted tank would give to the algae. What is your lighting situation and are you running co2consistantly during the day.


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## Sunstar (Sep 17, 2008)

Also that the co2 which isn't being used is essentially being wasted.. I am trying the on day off night now, been a week doing it that way too. So my experiance is minimum.


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## Manwithnofish (Mar 12, 2008)

I understand the biology of photosynthesis and all that. 

What I was trying to get at was the claim that "inconsistent" quantities of CO2 or CO2 fluxuations, (which serveral have testified) is a leading cause of algae outbreaks.

If you turn the CO2 off at night, as most people and the three of you seem to do, then you are obviously going to have CO2 fluxuations. It seems that one of these statements but not both can be true. By the way, I was turning mine off at night but I got the algae problem anyway.

Incidentally (don't want to redirect the thread to pH controllers but), how frequently does it turn the solenoid on and off say in a day, and have you observed it at night...if so, is it off at night or does it kick on and off?


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## houseofcards (Feb 16, 2005)

Your still seem to be looking at co2 as a vaccum on to itself. Yes co2 is important, but remember you could have algae free tanks without any co2 if you have a good biofilter, good plant mass and a light control. Don't look to just co2 as the answer. There is no basis that co2 has to be kept consistent 24/7 to avoid algae.


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## Manwithnofish (Mar 12, 2008)

So, I take it that you are of the opinion that you think turning it off is better than running it 24/7 in order to acheive consistent quantity of CO2. Don't read more into the question than is there. I realize that there are other important factors to be considered. I was simply asking for opinions on what most people do. Do you turn it off or run it 24/7?


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## Veloth (Jun 25, 2008)

Mine goes off 1 hr before the lights and comes on 2 hrs before the lights


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## freydo (Jan 7, 2006)

i keep my co2 on 24/7 without any problems to the fish, and i'm not too worried about the wasted co2, as i have a 20lb tank and it lasts close to 1 year if not more. of course i'm injecting at about 2bps into an inline reactor, which is fairly efficient at dissolving the co2 into the water. i would probably have to increase the bps by quite a bit before my fish start gasping.

however houseofcards is right about co2 not being the end all be all in terms of algae control. and btw... i just restarted my 65 gallon and dealing with green spot algae


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## Manwithnofish (Mar 12, 2008)

So are you saying that, all other parameters being at the "correct" levels, deviations of CO2 (too much or too little) in and of itself can't cause an inbalance resulting in algae?


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## Nevermore (Mar 26, 2007)

Manwithnofish said:


> So are you saying that, all other parameters being at the "correct" levels, deviations of CO2 (too much or too little) in and of itself can't cause an inbalance resulting in algae?


Bba or black beard algae can be caused by fluctuations in CO2.


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## Elohim_Meth (Nov 4, 2007)

I think deviation of CO2 level (rather too little than too much) that lasts several days - not intra-day - may cause plants suffering and consequently algae bloom.


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## Indignation (Mar 9, 2008)

I agree with houseofcards, most likely your algae bloom was caused by another variation in your tank. In my tank, a massive re-planting stirred the substrate enough i got a small ammonia spike that triggered a nightmare thread algae out-break. It took a month to get rid of. That said, having the right balance of co2 in place will help you get rid of the algae much faster. 
Most of my algae blooms can be traced to 2 things - not enough co2 combined with too much light, or ammonia spikes that the bio-filter couldn't convert fast enough, usually caused by me getting a little over-zealous with rearranging.

I turn my co2 on an hour before lights come on, and turn it off an hour before they shut off in the evening. The theory is the co2 builds up so the plants can use it the second light hits them, and it is removed (somewhat) before the lights go out for the sake of fish and shrimp. It seems to work very well for me, but YMMV.


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## houseofcards (Feb 16, 2005)

Manwithnofish said:


> So are you saying that, all other parameters being at the "correct" levels, deviations of CO2 (too much or too little) in and of itself can't cause an inbalance resulting in algae?


In a perfect world, yes. But how do you know all those other things are in balance. Just for the record I pretty much do what Indignation said in terms of running co2. I think what he said about algae is very true as well.

The point I was making is don't look to one variable as the cause. Many will simply look at co2. I have always looked at algae contol from an organic control content. If you have a fish heavy tank and or plants that aren't growin well, you probably have alot of organics in the tank. Once you go to medium/high light algae will have what it needs to get out of hand. If you attack it from both sides (getting the plants to grow and reducing your organic content) then your more likely to be successful in combating algae. So for example adding more plants/biomedia if possible, upping co2, adding seachem purigen and reducing lighting period (if your exceeding 7/8 hrs), reduce fish feeding is a multi-pronged attack on algae. If you do all these things and your fertilizing enough your algae issues will be history. I have 5 tanks and don't have any real algae issues in any of them. Control organics and controlling your light are the two biggies.


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## Manwithnofish (Mar 12, 2008)

Again, I realize there are other factors and I appreciate the advise. But I'm addressing the "wholistic" approach to the algae issue on another thread. I just wanted a side thread to get opinions on running CO2 24/7 or turning it off?

I think I have the answer.....one person runs 24/7 but at a slow rate...everyone else turns it on/off with lights.

Thanks for the replies.


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## freydo (Jan 7, 2006)

odd man out rogar-Si
oh well.


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## chagovatoloco (Nov 17, 2007)

Balance is the key word. Each system is different,in a high light tank with co2 injection an irregular co2 level during the photo period _may_ cause algae to grow. I know you are looking for exact answers but at times there aren't any. I don't do 24/7 co2 because it don't feel it is needed. My plants grow and algae is at bay. You don't need max level co2 just consistent, plants do adapt and it is easier to adapt if parameters stay consistent.


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## jmhart (Nov 13, 2007)

We had a discussion about this on the local plant club forum, and pretty much came up with saying that it doesn't matter one way or another. We were pretty split, 50/50, on those that turn it off at night and those that don't.

No noticeable difference except longer lasting cylinders.

To note, I have been turning my co2 off at night since day 1. Off at lights off, on 1 hour before lights on.I now use a pH controller(didn't for a long time), and something that's worth noting is that my pH doesn't rise dramatically at night. My target pH is 6.4, but once co2 goes off, the highest it reaches at night is 6.7. If I leave it off(say during a blackout or something) pH rises to 7.4. 

Point is, there is still a good amount of carbon available at night, plenty considering it's not even used.


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## Manwithnofish (Mar 12, 2008)

jmhart said:


> We had a discussion about this on the local plant club forum, and pretty much came up with saying that it doesn't matter one way or another. We were pretty split, 50/50, on those that turn it off at night and those that don't.
> 
> No noticeable difference except longer lasting cylinders.
> 
> ...


This is what I was wondering about. Great, and thanks for the reply.

By the way, just curious about the pH controller. Do not notice the CO2 is "on" much more during the day? Is the controller turning it off at night? And is it like off all night, hours at a time or is the difference just that the on/off intervals are shorter during the day than at night. Curious to know your observations.


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## jmhart (Nov 13, 2007)

Manwithnofish said:


> This is what I was wondering about. Great, and thanks for the reply.
> 
> By the way, just curious about the pH controller. Do not notice the CO2 is "on" much more during the day? Is the controller turning it off at night? And is it like off all night, hours at a time or is the difference just that the on/off intervals are shorter during the day than at night. Curious to know your observations.


I have my solenoid plugged into the controller plug, plugged into the timer....so at night my co2 is completely off. The pH controller box is on(since it has it's own power source) and continues to read the tank pH(all the way up to 6.7).

Because of crappy needle valves, before the pH controller, I have my co2 set to a decent level, but had my spray bar disturbing the surface. This allowed me to have the "right" amount of co2. Now with the controller, I've set a faster bubble rate(and lowered the spray bar), so the amount of time spend "on" (as controlled by the controller) is reduced, and I save the slightest amount of co2 via the controller.

Via the timer, my co2 is off completely from 10pm until 11am the next morning.


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## Complexity (Aug 11, 2008)

I want to make a simple correction. I do not turn my CO2 off at night. I use a pH controller to manage the CO2. I have a TEK T5 HO fixture with 2.88wpg, and with that much light, I wanted to not worry about the CO2 levels fluctuating. I simply set the pH controller to what I want and walk away. My plants grow very well, the BBA I got from a forum purchase has disappeared, and my fish are doing great. I'm dosing at least 30ppm, most likely more.

I can't say if the pH controller is off all night since there's no reason to check it. But I've heard the regulator kicking on or off late at night (wee hours of the morning?) so I don't think it stays off all night, every night.

Keep in mind that things, such as a water change, can cause the pH controller to kick on more than normal to get the CO2 leveled out again. Also, as new plants are added to the tank and as all the plants grow, they will use more CO2 than before so that makes the pH controller kick in even more to keep up. Further, the bps setting will determine how often and how long the pH controller will need to stay on to maintain a certain CO2 level. For example, when using a slow bps rate, let's say 1 bubble per second, it's going to take longer to build up the CO2 to match the chosen setting. If I set it to a much faster rate, let's say 5 bps, then the pH controller will need to turn on and off much more often since it is pouring out so much more CO2 when it is turned on. It's even possible to force the pH controller to be on almost al the time if the bps setting is so low that the CO2 injected is less than what the plants are using.

So it's hard to give a definite answer as to how often or how long a pH controller turns itself on or off. All the pH controller does is maintain a stable CO2 level, but it requires that the operator works with the bps to find the right level of dosage when the pH controller is on.


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## StevieD (Sep 23, 2008)

I've noticed very little activity from my controller at night, it will come one a few times, but it is definitely more active during the day. To my surprise it is off most of the time. Don't know overall if a controller is more efficient that a solenoid with a timer and turned off at night. 

As already said fluctuations in co2 is only important during the light period as co2 really isn't need when lights are out. If you keep the co2 consistent during the lighting period and it drifts at night, that is ok, if it varies too much during the lighting period, this is bad.

Flow is often a cause for algae to breakout in areas of the tank. Co2 can vary greatly in different areas of the tank, and if there is adequate flow throughout the tank, the co2 will naturally be more consistent. This is very important and often overlooked. You can install powerheads to increase the flow around the tank. 

One thing where co2 controllers really benefit is during the lighting peroid, depending how much light is used the plants uptake more co2, and if you have something like a noon burst, without a controller it does not make up for this as it is just supplying a steady amount. This to me will cause some varying levels during the day. A controller will deliver more co2 when it is needed, as the plants use it up. 

I'm starting to think that using a controller has the benefits of steady co2 delivery and a reduced chance of algae breakout, but i don't have any proof. I haven't had any algae problems in two tanks, which isn't much proof, but many of the algae threads are from people with DIY co2 and pressurized co2 on a timer. My system could just be well balanced, and you certainly don't need a controller to have an algae free tank, any balanced system will work, but for the beginner, i believe the controller could be a help until one gets good at balancing their system. Again not really proof, but just a theory. 

Stevie D


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## jmhart (Nov 13, 2007)

Complexity said:


> All the pH controller does is maintain a stable CO2 level, _but it requires that the operator works with the bps to find the right level of dosage when the pH controller is on.[/_QUOTE]
> 
> I disagree, to some degree. It's of course possible to dramatically overshoot the bubble rate and cause issues, but within reason, the bubble rate doesn't matter so much if you are using a pH controller. Once the pH is hit, gas is off. Fast bubble rate(again, not obscenely fast or anything) just means the pH drops faster. Too fast of a bubble rate and it can't all get diffused without being wasted, but as long as you are below that point, the pH(and therefore the co2 level) remains at the target level no matter what the bubble rate.
> 
> So, I guess my disagreement is really also an agreement. Bubble rate does factor in to some degree, but it's a pretty wide range.


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## Complexity (Aug 11, 2008)

jmhart said:


> So, I guess my disagreement is really also an agreement. Bubble rate does factor in to some degree, but it's a pretty wide range.


I think that's a fair comment. It's not as if the bps has to be set at some perfect rate, but the results of setting it at either extreme of being much too low or much too high makes it harder for the pH controller to work at its best.

When I first set up my pH controller, my main problem was setting the bps too low. So I'd see the controller almost always on with the pH higher than my setting and the drop checker remaining green (as opposed to yellow). On the other extreme, I've raised the bps much too high to where I had more of a problem getting it all diffused via the reactor so I lost CO2 to bubbles while the pH controller was constantly going on and off, trying to keep the CO2 level. After a few adjustments, I finally found a nice happy medium in which the pH controller is easily able to maintain the pH setting I've selected.

A good way to look at it is similar to what happens with an air conditioner in which turning the a/c to 60° while attempting to maintain a temperature of 75°. When the a/c is on, the air is too cold, making it difficult to maintain a steady 75°. So the a/c must turn on and off very often to try to keep the temp at 75°. And visa-versa, it's virtually impossible to maintain a 75° temp if you set the a/c to 85°.


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## Manwithnofish (Mar 12, 2008)

jmhart said:


> I have my solenoid plugged into the controller plug, plugged into the timer....so at night my co2 is completely off. The pH controller box is on(since it has it's own power source) and continues to read the tank pH(all the way up to 6.7).
> 
> Via the timer, my co2 is off completely from 10pm until 11am the next morning.


I'm not sure I understand what your saying. Your solenoid switch is plugged into a timer that turns it off at night, so what's the point of the pH controller....is only working durning the day when the solenoid is turned on?

As for the other post,


> For example, when using a slow bps rate, let's say 1 bubble per second, it's going to take longer to build up the CO2 to match the chosen setting. If I set it to a much faster rate, let's say 5 bps, then the pH controller will need to turn on and off much more often since it is pouring out so much more CO2 when it is turned on. It's even possible to force the pH controller to be on almost al the time if the bps setting is so low that the CO2 injected is less than what the plants are using.


 that really made a lot of sense to me and cleared up much regarding this issue. Thanks for the explanation.


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## StevieD (Sep 23, 2008)

There does seem to be an area where the controller is more efficient. I try and set mine so the co2 only needs to stay on for like 20 minutes or maybe a little longer and then it stays off for about an hour or longer. At night it hardly comes on. I set a .06 hysteresis so there is a little fluctuation so the controller isn't always coming on and shutting off too frequently. 

Stevie D


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