How accurate are "inexpensive" dissolved oxygen meters and reagent kits (by modified Winkler titration).

[David3147]

Pondering, in the name of curiosity, getting one of these.
1) are they accurate?



or

HI3810 Dissolved Oxygen Test Kit

The HI3810 is a chemical test kit for the determination of dissolved oxygen.

www.hannainst.com

Purpose is to see if, in my tank (undersized skimmer, large surface area to volume ratio), a recirculation skimmer will lower dissolved oxygen meaningfully. My plan may be to run the recirculation CO2 scrubber at night and as a room air CO2 scrubber during daytime.

Secondary questions, and prob deserving of separate threads:
2) In my set-up, does a skimmer really contribute that much oxygenation? (undersized skimmer, large surface area to volume ratio)

3) Is fish respiration a far bigger contributor of CO2 in the water column (vs ambient air) And is it possible that these recirculation CO2 scrubbers are really just extracting CO2 from the water. (bubbling water into the skimmer, releases it's CO2 and then it's scrubbed?)

I know there is concern of recirculation CO2 scrubbers starving a tank of fresh ambient oxygen. But in certain set-ups (such as mine), maybe the skimmer really does not function to oxygenate substantially. Happy to run the experiment. Current fish load is low, and could be fun to run the experiment as more fish are added to the system.

 

[Randy Holmes-Farley]

I don’t know how accurate they are, but I think it likely they have reasonable ability to compare two solutions, one saturated and one in question.

 

[livinlifeinBKK]

Perhaps I don't know quite enough about the Winkler Method (which is completely possible), but how can a probe replicate the Winkler Method remotely closely?

 

[Malcontent]

Measuring Dissolved Oxygen - Environmental Measurement Systems

Electrochemical or optical dissolved oxygen sensors are the modern and precise way to measure dissolved oxygen. Colorimetry and titration are other methods.

www.fondriest.com

 

[livinlifeinBKK]

Measuring Dissolved Oxygen - Environmental Measurement Systems

Electrochemical or optical dissolved oxygen sensors are the modern and precise way to measure dissolved oxygen. Colorimetry and titration are other methods.

www.fondriest.com

I'd never advise any hobbyist to perform the Winkler Method personally because they aren't trained to do it with the precision needed. I'd advise a hobbyist to use a meter as well.

 

[Randy Holmes-Farley]

FWIW, I was referring to the meter.

No, the meter does not use a method similar to a kit.

I would not have confidence in seeing small differences with a kit.

 

[Dan_P]

FWIW, I was referring to the meter.

No, the meter does not use a method similar to a kit.

I would not have confidence in seeing small differences with a kit.

The Winkler chemistry implemented by Hanna gives consistent results. It does require care in not introducing oxygen into the sample. I have been able to modify the test to handle 12 mL samples. This indicates to me that the chemistry and not accidentally introducing O2 are within reach of the average person. I think differences of 0.5 ppm O2 can be reliably detected but I would not rely on the method to detect 0.1 ppm differences.