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CO2 Questions

Discussion in 'CO2 Enrichment' started by shane, May 16, 2008.

  1. shane

    shane Lifetime Charter Member
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    Currently, I have the CO2 come on 1.5 hours before the light and turn off 1 hour before the lights turn off.

    I am assuming we would like to get the target 30ppm of CO2 in the tank by the time the lights come on? If I reach 30ppm of CO2 in the tank after the lights have been on for 4-5 hours; would this be considered bad?
     
  2. ceg4048

    ceg4048 Lifetime Charter Member
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    Hi,
    Because we are not able to measure CO2 accurately (unless we buy $500 lab equipment) it is not an automatic given that gas on at 1.5 hours before lights on achieves 30ppm, however it'll be higher than if the gas were turned on later. If 30ppm is achieved later than lights on this is not as good as it can be but it may not be as bad as it can be either.

    The bottom line is that you want the CO2 concentration to be as high as you can get it as early as you can get it with respect to lights on.

    Cheers,
     
  3. Mooner

    Mooner Lifetime Charter Member
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    My CO2 is on 2 hours before lights on and off 1 hour before lights out. According to the DC, 30 ppm is achieved at the 2-3 hour mark after lights on.
     
  4. tedr108

    tedr108 Lifetime Charter Member
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    Shane,

    I turn my CO2 on 1 hour before lights on and turn it off one hour before lights off.

    You do not mention how you measure CO2 ppms. Most of us use drop checkers -- good combination of accuracy and cost-effectiveness. When using a drop checker, however, there is a delay in the sense that by the time your drop checker registers green (30ppm typically), it is showing you a snapshot of like 2 hours ago, I believe.

    I've been doing well with my CO2 -- I start it at 8:00am. My drop checker doesn't register pure green until about noon. That's a little longer than I had hoped, but overall my tank is doing well, so I think all is fine. I purposely picked the absolute worst place in my tank (flow-wise) to put my drop checker. That may have something to do with my delay.
     
  5. shane

    shane Lifetime Charter Member
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    Hi tedr108,

    I use a drop checker with 4kDH liquid. I have a pH meter in my tank. I believe I get about 30ppm CO2 at around a pH of 6.6. In the morning, I typically see a pH of about 7.2 or so. The tank gets to a pH of about 6.6 after 4-5 hours of the lights being on.

    Using both a CO2 reactor and mister at the same time.

    I am thinking about hooking up to my pH controller and setiting it to a pH of 6.6. This would allow 30ppm of CO2 all the time. Not sure if that is great for the fish or not.
     
  6. tedr108

    tedr108 Lifetime Charter Member
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    Hi Shane,

    How is your tank doing? Good plant growth? Any algae?

    If you are not having problems, you may very well be getting plenty of CO2 already.

    I'm not sure I would trust a pH controller. The cheaper ones can have issues, and I sure wouldn't want one to kill off my critters one day (or nite).
     
  7. shane

    shane Lifetime Charter Member
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    I have some BBA on some Anuibius and some green algae here and there. So the tank could be doing better. Growth seems to be good. Just put some Rotala Colorata in last week and has grown at least 5". Its the anubius that has always had problems (BBA).

    I have a Dupla Alpha pH controller have had it for about 5 years. No problems so far.
     
  8. Carissa

    Carissa Guru Class Expert

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    If your tank pH is continuously dropping for the first 5 hours, it is indicative of changing co2 levels. The exact level is not as crucial as the stability of that level. Reason being that plants adapt to the level of co2 they are exposed to on a regular basis, when the level is below what the plants have adapted to, the plants don't grow as well and algae starts. It can take weeks for plants to readapt to a lower co2 level. I think it would be better to maintain the same amount of co2 at all times while the light is on than to have it fluctuating. This would also explain why new plants seem to grow better than plants that are already in the tank, perhaps they are not adapted to high co2 levels before they are put in, in which case all the extra co2 just translates into extra growth.

    I have had trouble with anubias and algae more so than other plants, probably because they are slower growing. I dip mine in a weak bleach solution to kill algae when it gets out of control.
     
  9. Gerryd

    Gerryd Plant Guru Team
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    Shane,

    Try shading your Anubias more. I have found that helps with algae on these plants, assuming there is no other underlying cause.

    What type of lighting are you using?
     
  10. shane

    shane Lifetime Charter Member
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    Gerryd,

    I am using 150Watt's of power compact's; 6700 bulbs. 9 hours per day on time.
     
  11. shane

    shane Lifetime Charter Member
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    In terms of using a pH controller set to a pH of 6.6 to get 30ppm of CO2, would it be better to connect the pH controller to a timer that turns on the controller 1-2 hours before the lights come on and turns off 1 hour before the lights turn off?

    This way one could get lots of CO2 into the water before the lights turn on and not have too much CO2 in the water to gas the fish later on in the day.

    How much CO2 can one add to the water in a certain amount of time with no ill affects to the fish?
     
  12. VaughnH

    VaughnH Lifetime Charter Member
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    A pH controller set to 6.6 pH will not necessarily set the CO2 concentration to 30 ppm. In fact the only way to determine what pH will give you 30 ppm in the tank water is to have a drop checker in the tank, then measure the tank water pH when the drop checker tells you you have 30 ppm of CO2. Then you can set the pH controller to that pH and it should ensure that you have 30 ppm in the tank for a few days, or until the tank water conditions change enough that it would take a different pH to get 30 ppm.

    Actually, you still wont know you have 30 ppm - it could be anywhere between about 20 to 45 ppm, depending on how well you can judge the color of the drop checker.
     
  13. shane

    shane Lifetime Charter Member
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    Hi VaughnH,

    I used a drop checker (I have 2 - a normal and dual chamber CalAqua) to determine the pH where the drop checker is green (both chamber are equal in color in teh cal aqua case).
     
  14. VaughnH

    VaughnH Lifetime Charter Member
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    My point is that the tank water pH and the drop checker water pH are not likely to be the same.
     
  15. shane

    shane Lifetime Charter Member
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    Hi VaughnH,

    Does the pH of the water in the drop check matter?

    If the drop checker shows the 2 chambers are equal and that signifies 30ppm CO2; I can't just look at the pH that my pH controller shows at that time and call that the pH that correlates to 30ppm CO2 (for that specific time at least)?

    Or are you saying that there is an error in the CO2/drop checker solution interface that can cause the CO2 to be off of 30ppm even though the drop chacker shows green?
     
  16. VaughnH

    VaughnH Lifetime Charter Member
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    The problem with any CO2 measurement based on measuring pH, which is what a drop checker does, is that the concentration of CO2 is proportional to one over ten raised to the pH power. That means a very small error in pH makes a big error in ppm of CO2. About the best we can do judging color is +/- 0.1 in pH. That corresponds to an error (assuming about a 6.6 pH, and 4.0 dKH hardness) of +8/-6 in ppm. Most people are going to be off more like +/-.2 in pH, which gives an error of +18/-11 ppm. So, if you are real good at seeing colors, your 30 ppm reading could be 24 to 38 ppm. If you are closer to average in seeing colors, your 30 ppm reading could be 19 to 48 ppm. The dual chamber drop checker, which I am using now is a big improvement, assuming the reference bulb color remains stable for a couple of weeks. But, I still doubt that we can avoid that +/- 0.1 pH error. I always say I have about 30 ppm because I am aware of that built in error.
     
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