Reading Test Kits

[Dave Cushing]

I use the Aquarium Phamecuticals test kits for everything except phosphate. My question is, how do you do your color matching?

If I look through the side of the test tube (I'll use Nitrate as an example), I read ~15ppm, if I look down through the tube, the reading is closer to 40 ppm.

In my Dry-Tab phosphate kit, it says if you have trouble reading to look down through the tube, the Aquarium Pharmecuticals does not.

So what is the normal way to read it?

Thanks

Dave

[Matt W]

On my Aquarium Phamecuticals tests I hold the test tube against the white of the card and look through the side of it, with the white behind it. Has always seemed to be accurate to me that way.....

[Cearbhaill]

I hold it up against a white kitchen cabinet, then I hold it up to the kitchen window, then I walk over to a larger window and look down from the top, then I ask my husband whe he sees.
Majority rules.

[anonapersona]

I only test during the daytime and I stand at the window. I hold the tube 1/2 inch away fromthe whit edge of the card.

Sometimes it is difficult, sometimes I have to stop and look very hard to see if there is any purple in the red, or any blue in the green, or whatever the color graduation is supposed to be. You are looking for color, not intensity, typically.

If I stand at the sink under the incandescent lights, there will be a huge difference in the apparent color.

[RClarkofNC]

I do it as Matt W. described and that seems to work pretty well for all of my tests except for O2. With that, I'm trying to decide between several close shades of pink. So I wrote Tetra and here's what they said...

_________________
US Tetra Consumer <USTetraConsumer@tetra.net> wrote:
From: US Tetra Consumer
Subject: RE: Question about reading O2 test results

Thank you for your inquiry. Hold the vial against a light background, like
a white wall or piece of paper. Place the color card next to the vial and
compare.

Regards,
Tetra

-----Original Message-----

I have a questions about interpreting the results of
your O2 test. When comparing the vial to the color
scale card, what is the proper distance between them?
I've noticed that when the vial touches the card, the
vial appears a much darker pink than when it is held
even slightly off of the card, with the vial appearing
lighter and lighter as it is moved away from the card.
Since the shades of pink on the color card are so
close together, determining the exact shade of pink in
the vial has a significant impact on the
interpretation of the results. So I want to make sure
I am doing it properly.