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Oxygen test kits

Discussion in 'General Plant Topics' started by scottward, Dec 18, 2011.

  1. scottward

    scottward Guru Class Expert

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    ** Dumb question alert **

    Oxygen test kits - as opposed to using a DO meter - are there any good ones?

    I'd like to know if my tank is saturated with O2...can I get a reasonable result from a simple test tube/paper strip test kit?

    Scott.
     
  2. scottward

    scottward Guru Class Expert

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    And I put the dumb question alert because I think the answer is going to be "no" (hence the threads discussion electronic DO meters).
     
  3. Florin Ilia

    Florin Ilia Lifetime Charter Member
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    I have the Tetra O[SUB]2[/SUB] test that Dutchy mentions in the other thread... and also a DO meter. I could maybe do a parallel test to see if they're in the same ballpark.

    Of course that would be me testing with my reagents, my hands and my eyes... how relevant that would be for you I'm not entirely sure.
     
  4. scottward

    scottward Guru Class Expert

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    Thanks for the reply Florin.

    It would be interesting to see how accurate the reagent test is.

    A glass of tap water that has been left to sit for a while will hold a known amount of O2. Could you take the temperature of the water and perform the reagent test?

    I'm not familiar with the colour scale of the reagent test, but I know that some of them are horribly difficult to use.

    Scott.
     
  5. Florin Ilia

    Florin Ilia Lifetime Charter Member
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    OK, my chemical test kit is actually Salifert, not Tetra as I remembered (http://www.marinedepot.com/Salifert_Dissolved_Oxygen_Test_Kit_Specialty_Test_Kits_for_Saltwater_Aquariums-Salifert-SF1131-FITKSI-vi.html).

    I performed an extensive study which consisted of 2 measurements :), each done with my DO meter and with the Salifert kit.

    Measurement 1. Aquarium water that sat in an open glass for about 8-10 hours in my living room

    DO meter said: temp 23.4°C; O[SUB]2[/SUB]=7.51ppm (89.7% saturation)
    Salifert said:
    [​IMG]


    Measurement 2. Water straight out of the tap

    DO meter said: temp 19.4°C; O[SUB]2[/SUB]=9.60ppm (106.4% saturation)
    Salifert said:
    [​IMG]

    I did not edit the pics except for cropping.

    My conclusion: this kit and/or my measurement skills suck. In the second measurement the color is a different hue than the chart.

    YMMV.
     
    #5 Florin Ilia, Dec 20, 2011
    Last edited by a moderator: Dec 20, 2011
  6. scottward

    scottward Guru Class Expert

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    Florin,

    Thanks for taking the time to do that! That was nice of you (because it's Christmas hey??) :D

    I think the test kit sucks (as a lot of them do).

    From what I've been reading it seems most fish need at least 5ppm- but look at the difference between 4 and 6 on that colour chart - as if any human being would be able to tell the difference there.

    And I would bet that most other brands of O2 test kits would use the same colour graduation.

    About the only test kit that I own that is actually useful is the GH/KH test kits that I have, as these kits show a very obvious change in colour (e.g. from blue to yellow). All the other kits that rely on comparing to a colour chart aren't so good.

    Scott.
     
  7. Paul G

    Paul G Lifetime Charter Member
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    I have been using the Salifert test and have been consistently getting near 100% saturation results. Having recently noticed some respiratory distress in some fish at night, I have tested at these times and gotten high enough results that I could not account for it. It occured to me that once you take the sample, adjust the level in the vial, add reagent and shake - at least twice - you have inevitable increased the oxygen solution from its original, real, value.

    I purchased a Pinpoint II O2 meter about a month ago and started monitoring full time. Readings from this device are always much lower than the reagent test results, and have been so low in the last few days that I am not believing it. I adjusted pump outputs and so forth to get a good deal more ripple, even some "chop", at the surface and stopped the problem with the fish, but the meter reads lower than I think it should. I'm thinking a recalibration is needed.

    I have ordered a Lamotte O2 kit and will sharpen my lab technique, and, if necessary, I will obtain another O2 meter as well (any recommendations?). I will cross-check results until I get it figured out.
     
  8. Tom Barr

    Tom Barr Founder
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    The test kits are poor because they might be off 1-2 ppm of O2.

    If so......then you miss the effects, you also miss the changes over a day cycle unless you test every hour etc.

    I could not determine the differences between the wet/dry and the canister filter for example, since the difference was 1-2ppm, but the error with the meter was EXTREMELY small, vs the test kit.
     
  9. Florin Ilia

    Florin Ilia Lifetime Charter Member
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    I use the Hach LDO sensor, which I bought when I was in "measurement craze" mode. It's really really expensive, I'm glad that I have a good device but today I wouldn't spend that amount just for this.

    A friend is using the JBL chemical O[SUB]2[/SUB] test, I will ask him to do a parallel run with that and my sensor, and I'll post back the results.
     
    #9 Florin Ilia, Dec 21, 2011
    Last edited by a moderator: Dec 21, 2011
  10. Florin Ilia

    Florin Ilia Lifetime Charter Member
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    New parallel run with the JBL test. The testing procedure seems more reliable in the sense that the sample is not agitated when in contact with the air.

    Measurement 1. Tap water that sat in an open glass for about 24 hours in my living room

    DO meter said: temp 23.3°C; O[SUB]2[/SUB]=8.22ppm (97.2% saturation)
    JBL said:
    [​IMG]


    Measurement 2. Water straight out of the tap

    DO meter said: temp 16.2°C; O[SUB]2[/SUB]=10.25ppm (105.1% saturation)
    JBL said:
    [​IMG]


    Measurement 3. Water from my Betta tank

    DO meter said: temp 29.4°C; O[SUB]2[/SUB]=7.12ppm (93.9% saturation)
    JBL said:
    [​IMG]


    I did not edit the pics except for cropping.

    My conclusion: this kit seems slightly better than Salifert in my limited testing but still a 1 ppm difference seems hard to spot.

    YMMV.
     
  11. Tom Barr

    Tom Barr Founder
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    JBL kit is better, but........you really are missing about the 2 ppm in between range, only a colormetric or a meter will help there.

    The LDO's are very $$ but I got some used.
     
  12. scottward

    scottward Guru Class Expert

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    Thanks for the info and the help.

    I know that at 30 degrees O2 can saturate at 7.56mg/L.

    With a good surface ripple is it most likely that I'm at this level anyway? Or would this only be truly possible if I didn't have the canisters and the fish and/or really splashed the surface around a lot?

    Scott.
     
  13. Paul G

    Paul G Lifetime Charter Member
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    O2 and CO2 test kits from Lamotte

    The LaMotte DO test kit is very cool! You can "fix" the sample so that the you needn't worry about O2 changing during the titration. You get enough sample to perform the titration twice, so you can check yourself. I get within .2 ppm each time I do this.

    I could not properly recalibrate the Pinpoint monitor without changing the membrane and fluid. Even then, the recalibration process seems very "hinky" to me, as it is difficult to duplicate settings for the same value and it's hard to know how much time to allow for the probe to stabilize. The thing appears to drift. It seems to me I am doing this according to the directions, but I have trouble believing the numbers I am getting.

    After I recalibrated the monitor as best as I could, I did the reagent test with the new kit only three days later, sampling the water right next to the probe.

    Monitor says 3.8 ppm. LaMotte says 4.8 ppm. Hmmm... I think the reagent kit is right.

    I am going to set the monitor value where the LaMotte reagent kit tells me it should be, and test regularly to check for drift. This isn't the prescribed manner of calibrating the meter, but should be an interesting experiment.

    Hanna Instruments has a portable DO meter advertised as a field professional aquaculture tool at a decent price. It uses a galvanic probe said to be "faster" than the polarographic type. Anyone have comments on this?

    I also got a CO2 kit from LaMotte that uses a precision titration method. I have been trusting that my reconstituted RO makes it possible to believe in "The Table". I have a KH of 116 ppm (6.5 d) and a pH of 6.84. The table says I should have approximately 28 ppm CO2. The LaMotte kit gives me 28 ppm.

    I highly recommend both of these kits. These are professional-use titration method kits. Instructions are clear, the color indications are positive with no guessing, so you get precise, accurate results, and you can purchase replenishments seperately.

    Regards, Paul G
     
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