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Discussion Starter · #1 ·
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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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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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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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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Discussion Starter · #5 ·
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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Discussion Starter · #7 ·
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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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 :p
 

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Discussion Starter · #10 ·
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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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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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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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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Discussion Starter · #15 ·
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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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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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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Discussion Starter · #19 ·
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.
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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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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