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Basic CO2 question i hope!

Discussion in 'CO2 Enrichment' started by Gbark, Jun 15, 2009.

  1. Gbark

    Gbark Guru Class Expert

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    Hi All,

    First post for me, and i wish to jump in with a question that has probably come up before.

    I have a small 70ltr planted tank, with a few small fish. I have had the setup now for about 10mths.

    I used to have a yeast fermentation CO2 system, which was constantly supplying co2 day and night. Everything has been fine, plants healthy, fish healthy.

    So i have just upgraded to a co2 cylinder and solinoid valve. Since installing i have algee growing and my dropper never turns light green (always dark greeny/blue)

    My question is should i let the co2 solinoid valve switch on/off with my lights and increase the bubbles or should i leave it on 24/7.

    Thanks in advance
     
  2. Tom Barr

    Tom Barr Founder
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    No good reason to use CO2 at night.

    Add more during during the day time only.
    Be careful, patience and increase it carefully and slowly.

    Watch plants, fish etc carefully, add a bit more progressively and then watch.
    Do not add more then wander off for the rest of the day...........

    Regards,
    Tom Barr
     
  3. argnom

    argnom Guru Class Expert

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    Well Tom, for the firt time ever, in all the forums where I've seen your posts, I have to say I disagree. Please don't get mad at me. :D

    When I firt setup my CO2 cylinder I used the selenoid valve to shut off CO2 during the night, I used a drop checker to make sure I had enough CO2 also. Well, I was more worried about having too much CO2 than not enough to tell you the truth so I checked on the drop checker before lights out. After a day of tweeking green, a little on the yellow side! Yay!

    One morning, I decided to check the drop checker in the morning. Dark blue.

    The dude at my LFS told me to shut it off at night to avoid PH swings. After all, plants do not consume any CO2 during the night. Well, it seems that by turning it off, I was getting huge PH swings, so I decided to keep it on at all times. I reduced my bpm count by almost half and low and behold! Green before lights on and green before lights off! Yay! My PH probe also confirmed that the PH was stable.

    I have really soft water and my filter is way overpowered for my tank, so that probably is a factor for the PH swings at night woth no CO2. Even though the plants did not consume any CO2, the water just degased overnight.

    Bonus: After keeping the CO2 on 24/7 for a month, pretty much all the BBA in my tank was gone! Hurray!
     
  4. VaughnH

    VaughnH Lifetime Charter Member
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    I agree that you get bigger pH swings by using the solenoid valve to shut off the CO2 when the lights are off, but that pH swing isn't a problem for the tank inhabitants. When the CO2 runs 24 hours a day, at near the maximum concentration in the tank during the day, the pH will drop further when the lights go out, because the plants will no longer be using up the CO2. That can raise the concentration beyond what the fish can tolerate. So, in my opinion, the safest way is to shut off the CO2 when the lights are off.

    If you maintain a good amount of water surface ripple all of the time, I suspect you lose enough CO2 from the water surface to make the CO2 concentration stay within acceptable limits. I ran my tank that way for several months, and didn't see any difference it made to either the plants or fish.
     
  5. GTR

    GTR Prolific Poster

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    I've not been in this very long at all and this is one of the questions I've had as well.

    I'm using a controller to reduce the likeness of too much CO2. Controller is set at 6.9 and it will come on at all hours of the night. The other night I pulled the plug on the solenoid at lights off. pH was at 6.9. Next morning the pH was at 7.5.

    Are you saying that pH swing is acceptable? It would take roughly 1.5 hours once the CO2 was turned back on to bring the pH back down. 90g tank with a DIY reactor.


    Thanks,
    SteveU
     
  6. captain_bu

    captain_bu Prolific Poster

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    As VaughnH has pointed out pH swings induced by CO2 are not a problem for fish or plants. The TDS (total dissolved solids) in the water remain the same... if you were getting pH swings from changes in TDS (fluctuations in hardness) it would be a problem for the tank inhabitants since fluctuation in TDS can cause osmotic shock.

    There is no need to run CO2 24/7 even if it isn't causing problems for your fish... your plants can't use the CO2 at night and you are just wasting gas. If you want your CO2 levels to be at 30ppm when lights come on have a timer turn on the CO2 an hour to hour and half before lights on.
     
  7. GTR

    GTR Prolific Poster

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  8. Tom Barr

    Tom Barr Founder
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    So was it due to the improper use of CO2 when the lights where on, eg your fault for not adding enough to begin with and keep it there, or is honestly due to adding 24/7 or anything remotely to do with pH?

    I have far more wiggle room and buffer when I add CO2 only 10 hours of the day, vs chronic high levels 24/7. When the high CO2 is added, I alos have higher O2 levels to compensate. This aids and helps fish stress, respiration etc.

    Algae is relatively easy to deal with and kills nothing really, CO2 can and does kill more fish than any other thing in planted tanks where it's used.

    Neither my tanks nor Amano's ever uses CO2 at night. They do not have BBA either:) So it's due to not adding CO2 24/7, the observatioins that we all know cannot explain your claim and also support what myself, Amano and others also see.

    You are certainly welcomed to disagree, but why don't I or Amano also have BBA?
    Skill? Maybe a tad, but more likely good usage of CO2.

    I do not add for respiration and over dosing issues should it keep running 24/7 and when I sleep and do not keep an eye on the tank.
    I also use 60% less less gas refills than 24/7 users.

    Folks that add not enough to begin with during the day often have plenty of CO2 at the start of the day if they leave it on 24/7. If they do not do that, then the first few hours are lean/poor CO2 when the lights come on, so they get soem algae and other issues.

    If they added more CO2, had better current, responsive CO2 diffusion etc, then adding CO2 only during the day is not an issue.

    Still, this is not an issue of pH, never was. Nor an issue of "stability" whatever that means, it's simply about adding enough CO2 during the day time.

    If you have to add it 24/7 to have it start off at a decent ppm and cannot figure out any other way to do it, then that's all you have to work with.

    But.............that does not mean others are wrong, nor explains why myself and many others have little issue adding it during the day only.

    I'd rather have the fish less stressed in terms of respiration.

    Regards,
    Tom Barr
     
  9. Liakern

    Liakern Junior Poster

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    So If Understand correctly co2 induced ph swing is not harmful to fish because theres no fluctuating levels of dissovled solids?

    I'm working on a reactor of my own design but the only real downside so far is turning it on and off... could the same effect of turning it on and off be achieved by turning on and off an air stone?
     
  10. VaughnH

    VaughnH Lifetime Charter Member
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    You can reduce the concentration of CO2 in the water by turning on an airstone or two when the lights go out. And, if the water surface is always rippled you lose more CO2 from that surface than without the ripple, so yes, you can reduce the concentration of CO2 at night without shutting off the CO2. But, why continue adding it when it just goes right out the top of the tank to the atmosphere? Why not just turn it off at night? Using separate tmers for the solenoid valve and the lights lets you start the CO2 flowing in plenty of time to build the concentration back up before the lights come on. That is a cheap thing to do, and it saves you the money and bother of having to refill the CO2 tank so often.
     
  11. Liakern

    Liakern Junior Poster

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    diy co2... The thing is My reactor take hours to stop injecting co2 and depending on the bubble rate quite some time to refill. I figure its just best to keep it runnin full steam to avoid "warm up and cool down" times...
     
  12. Tom Barr

    Tom Barr Founder
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    Well you answered your own question right there pretty much.
    You likely should get a good piece of CO2 equipment that is responsive, hours is not good :cool:

    See DIY versions in the article's section here, and increase the flow rate, consider a DIY needle wheel using a Rio powerhead, simple, takes a few minutes, highly effective and response times are minutes.

    Then you cannot blame the equipment;)

    CO2 is key, so good responsive results are also key. This means higher flows, a method that rapidly disperses CO2 to the plants as fast as we can reasonably.
    The system you have is asking for troubles.

    Perhaps you can fanaggle it and get it to work, but why bother?
    The other solution suggested takes but a few minutes and makes the resultant far better and with much less labor, fiddling and risk.

    Given all the issues folks have with CO2, this focus/realization is critical to success over time.

    Try it and see for yourself.

    Regards,
    Tom Barr
     
  13. Liakern

    Liakern Junior Poster

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    I have very soft water. Ph swings from 7.0 to 6.6 because of co2. Is this ok? Or will my fish suffer from this? I heard mention thats its not the ph swing but actually TDS swing that cause fish harm.
     
  14. Gerryd

    Gerryd Plant Guru Team
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    double post.
     
  15. Gerryd

    Gerryd Plant Guru Team
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    Hi,

    PH swings ALONE WILL NOT CAUSE HARM to the critters.

    It is more kh swings that will cause issues.

    Anyone introducing c02 is causing ph swings and some very large.....

    If this was an issue, you can rest assured that noone would ever inject c02.

    Hope this helps.
     
  16. Liakern

    Liakern Junior Poster

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    I kinda figured that it had to be the case or noone would inject co2 in to very soft water like I have... I just needed the reassurance.

    Thank you Gerry...
     
  17. Gerryd

    Gerryd Plant Guru Team
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    No worries..........

    Many folk think this and is another big myth that persists.........
     
  18. Gbark

    Gbark Guru Class Expert

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    Ok peep's!!

    I have been controlling my CO2 to come on and off with my lights, and i have worked out i am getting a CO2 level of around 20ppm. My dropper has gone a nice green colour, YEY!

    I am going to add a timer to bring the CO2 on 1 hour earlier than my lights.
    Every thing looks well.

    G :)
     
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