Backyard Aquaponics
A place to discuss aquaponics

Hi guys.
Because I can tend to be a bit anal, and noticed a slight inconsistency, I measured my measuring devices.

I have 3 test kits.
NH - AquaOne
NO2 - Aquasonic
NO3 - Dr Wellfish.

They all have vials, and they all say to fill to the mark, or 5ml mark.

Aquaone's vial measures 3.6ml at the 5ml mark.
Aquasonic's vial measures 3.3ml at the 5ml mark
Dr Wellfish's vial measures 5.7ml at the top of the thick 'fill to mark'

What I would like to know, is are these kits tested? eg do they need to be 5ml, or are the chemicals matched to the 5ml mark on their vials.

In otherwords, I have 4 Dr Wellfish vials, that measure 5.7ml. Would it be better (I like them a lot more) to use these with the aquasonic and aquaone chemicals? I would certainly like to because Dr Wellfish uses narrow test tubes and the colour is easier to define.

You would probably need to do a benchmarking test across multiple brands and multiple trials to answer your question.

Or you could say forget the absolute numbers, and just measure the trends. The trends will be consistent within one brand of test.

did you measure to the bottom on the meniscus? In such a small vial that could make 1ml difference.

http://en.wikipedia.org/wiki/Meniscus

to the absolute bottom no.
Would the meniscus not make more of a difference in a larger diameter vial than a smaller?
This could be my mistake (I sucked at chemistry)
the vials that were out by the most were much wider than the Dr Wellfish, 19mm vs 8mm
there's a big change of area there by 4 times!
hmmmmm I will measure again then maybe I will be content they really are 5 ml, and then I can use the Dr well fish vials with the other chemicals :-) this would make me happy.

Thanks Skygazer.

A meniscus would make a bigger difference in a larger diameter because it is roughly a parabaloid, and depth will be dependent on its width (radius)

Yeah that's the simple way to rewrite my rambling tamo... I agree
Thanks

My vials are marked Dr Wellfish, the kit is Aquarium Pharmaceuticals. Filled to the mark (top of) and decanted into a Scherf test tube it was close as anything to 5mls.

yeah I did top of meniscus to top of mark, I can fix that from now on, besides I have a 1ml syringe and I can just could 5 of them. That's how I did my measuring, cos that's a lot more accurate.
Thanks for the tip Sleepe, I shall use the tubes from now on, they're much more convenient and the colour shows up better. my two spare tubes come from my GH and KH test kits, now redundant.

The size of the tube is immaterial if the test liquid has been calibrated to it - which is to be assumed.

Using chemicals from one set to another would work if the following was true.

1. the tubes were the same.
2. the comparison charts were the same.
3. the test liquids are the same.

As it is, you don't know if the tubes are the same, you have yet to report on the comparison charts (have you compared yet?) and so you don't know if the concentration in the test liquid is the same or if they are even the same chemical.

Not knowing enough about the test liquid, I wouldn't mix. After all, you were not buying tubes, you were buying a test and there is no reasonable expectation that you would combine with another test. You don't even know if they are using the same chemical as test liquid.

My thoughts too CRT - the chemicals (colour) would be matched to the amount dispensed and the diameter of the vials to go with the charts - mix and matching from different test kits would give different results (colours).

Different sized vials (diameter) will give different colour perception using the same liquid

If youve bought every test kit on the market and still arent happy with the results, maybe you should buy yourself an ion chromatograph!

Anyhow I bought the API Master test kit as recommeded by Rupert in some other thread here and tested a solution known to be 2.4mg/L NH4 and 1.6mg/L NO2 and I think it reads as good as can be expected. Havnt tried NO3 yet.

That's handy to know Brett

well done Brett, calibrating the kit

Yep, and we still haven't dealt with the refractory characteristics of the tubes yet.

...or the angle of the dangle being proportionate to the sag of the snag in time with the beat of the heat..........SNAG!!!! - sorry there SNAG