Oxygen (O2) Questions.......

Discussion in 'Freshwater Beginners' started by tommy jr., Apr 13, 2012.

  1. tommy jr.Valued MemberMember

    I have read that air stones do not put alot of O2 into a tank because the bubbles do not diffuse and once they hit the surface it escapes (similar to Co2 I assume).
    Many people say a hang off the back filter like an AC will do just as good if not better than an air stone.
    Still others suggest that it is water movement that provides the best O2.

    So I guess my question is, what does work best for getting extra O2 into the water?

    I ask because people have told me to add extra O2 to the water when my CO2 is not running. Seems like a good idea but I'm not sure the best way to accomplish this.

    It is a 180 planted tank with pressurized CO2 and several barbs, angels, tetras, lve bearers etc.
    Oh, and it has a Fluval FX5 with the outflow 2 inches under the surface in the middle of the tank. One output facing each end.

    Thanks in advance for your input!
  2. jdhef

    jdhefModeratorModerator Member

    Basically water get oxygenated thru an oxygen exchanged caused by surface agitation of the water. So both the agitation caused by a filter and the agitation caused by an airstone will allow the water to become oxygenated.
  3. catsma_97504Fishlore LegendMember

    All you need is a standard air line and air pump. By causing surface disturbance you will be gassing off CO2 and adding O2.

    Put your air pump on a timer to run during lights off and you'll be set.

  4. toosie

    toosieWell Known MemberMember

    If you are turning off your CO2 at night, I don't think you really need to add an airstone or other oxygen producing source. People that DO leave the CO2 running at night are usually the ones that benefit from adding an airstone set to come on a half hour to an hour before the lights go out and shut off again a half hour to an hour before the lights come on to offset the amount of CO2 the plants produce at night and help replenish the oxygen they consume. If you shut off the CO2 the minimal amount of surface agitation your filters produce is usually adequate.
  5. OP

    tommy jr.Valued MemberMember

    Yes I am going to run the CO2 on a solenoid that came with the kit so it will be off at night.
    So if it is only on durring the day, I don't need to worry about running a stone or other O2 booster?
  6. toosie

    toosieWell Known MemberMember

    I don't think you should really have to. I have mine hooked up to a pH controller that only allows CO2 to flow through when the pH is above a certain level, so when the plants are producing CO2, the pH controller just doesn't allow more CO2 to enter the fish tank from my CO2 tank unless CO2 levels start to decline. My controller making my CO2 unavailable would be similar to you shutting yours off, it's just that mine doesn't have to be on a timer and I don't have to use an extra airstone or powerhead or anything at night for my tank.

    Each tank is different, so the best thing for you to do is test your CO2 to see what the concentration is at, right before the lights go out. Then test it again an hour or two later to see if the CO2 concentration is getting lower (pH higher). If it isn't you can plug in an airstone or powerhead or something at that point. You can also test the CO2 concentration first thing in the morning before the lights come on to get a better idea what the CO2 does throughout the night. This is safety precaution because I don't want to lead you astray, but I personally don't know anybody that has to use an extra oxygen producing device IF they shut off their tanks before the lights go out.
  7. catsma_97504Fishlore LegendMember

    I have CO2 injection on a timer and DIY CO2 on my tanks.

    The high tech, injected system turns the CO2 gas on 1 hour before lights on and 1 hour before lights off. By doing this I am able to avoid having too much CO2 in the tank during lights out. I do not need to run an airline since I have found the correct balance in my tank.

    In my DIY CO2 tanks, I have to use O2 lines during lights out. This is because the yeast continues to produce gas and creates an issue for my fish. This is why O2 is needed.

    For your tank, you would need to determine the true pH of your tank water. Set some out in a bucket with an air line to gas off all CO2. In 24 hours, test the pH. This is the pH of the water itself.

    Then, also test your tank pH at varying points throughout the day. 1 hour before and after lights on; middle of the photo period; 1 hour before and after lights off. These changes in pH will give you an idea how much CO2 is in the water and how well your plants are taking in the carbon.

    You will also need to know your KH and GH levels. If the water isn't properly buffered the CO2 gas can kill your fish very quickly.
  8. pirahnah3

    pirahnah3Fishlore VIPMember

    I will say that actually fine bubble diffusion (which is what an airstone causes) is actually more beneficial to the introduction of oxygen into a tank of water than coarse bubble diffusion. We study this at great lengths in my work field.

    As far as how you get the air in there, the method stated above is correct the breaking of the surface tension actually allows the co2 to be gassed off and o2 to be taken into the water.
  9. bowcrazyWell Known MemberMember

    One large bubble of air doesn’t have the surface area that several small ones do. To put it simply the more surface area the more area for gas exchange whether it is at the surface of the column of water or the surface of the air bubble.

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