Colorimeters for water quality testing.

[Pices]

   Although there are many water quality test kits on the market suitable for aquaponics, they all seem to require matching colors to a chart to get a numeric value. Personally, I am absolutely terrible at matching these colors. Test equipment suppliers offer relatively inexpensive dedicated single chemical colorimeters and some offer multi-wavelength colorimeters that can test almost 100 different chemical compounds - many of which are of great interest to water quality and aquaponics monitoring. 

   Is there anyone on this forum who has experience using colorimeters to measure water quality parameters?  My question is are these devices accurate and repeatable? Are they subject to gross interference with real world samples? What are the draw backs to these devices? Do the reagents have very limited shelf life or require special storage conditions (such as refrigeration)? Would greatly appreciate any shared knowledge or experience with colorimeters.

[Bob Campbell]

I have wondered how a color blind person would be able to test their system.  I have used a program called Little RGB Color Picker 3.0.  It would be able to detect with very good accuracy the colors a test sample photo.  Of course this would require taking a picture and getting to the computer and then running the Little RGB Color Picker, and I expect someone with full color sight would have to help find the ranges.   But the program will give you 64000 different RGB values.

But this free program is not really free, because you must allow the download to install adware.   It's a pain in the ass, but you can remove their f---ing shit later with your security software.

I don't know of any other program that give you the RGB of a selected screen color, but if there are others you may wish to go that route.  It seems like a lot of work just to read the test results, but you got to do what ever it takes some times.

[George]

I think my color perception is normal but my test results don't match the colors on the chart very well.  I've never had a nitrate result match the chart. 

[Bob Campbell]

None of the test need to be accurate.  All you really need to know is where it's been and where it is now.

Ammonia starts at bright clear yellow and ideally that's what you want.  Nitrite starts at light sky blue.  Nitrate progresses exponentially from bright clear yellow toward red.   If it's yellow but you are not sure ask yourself if it's  a bright clear yellow or does it have some tint.   If so then it's probably 5ppm.   After you see the range first hand you will be able to pickup on the colors, Nitrate is not a major concern anyway.

If the the tests are near zero then all is good.  If they are not clear bright yellow or sky blue then you simply want to know approximately where it sits.  Exact reading can be difficult in the mid range on most of the tests, but all you really need to get is that the water has gone to a place where you need to take care of something.  For example if you can't tell the difference between 2ppm and 4ppm on the ammonia test it does not matter because you have too much either way.

George said:

I think my color perception is normal but my test results don't match the colors on the chart very well.  I've never had a nitrate result match the chart.