How Do You Determine The Api Test Colour?

[frogmarch1987]

So I recently started my fishless cycle but have come across I problem that I was hoping someone could answer for me.

When you have your test result from the API master kit, how do you decide on the colour of the water? I ask this because the colour is much darker when held right up against the card (due to it casting a shadow on the card) as apposed to when you hover your water a cm or 2 away from the card.

So what's the correct way to compare the colours of your water with the colour chart?

 

[james_fish]

I use the same white poster every week. On all of the tests, so it is fair.

James.

 

[curlyriff]

So I recently started my fishless cycle but have come across I problem that I was hoping someone could answer for me.

When you have your test result from the API master kit, how do you decide on the colour of the water? I ask this because the colour is much darker when held right up against the card (due to it casting a shadow on the card) as apposed to when you hover your water a cm or 2 away from the card.

So what's the correct way to compare the colours of your water with the colour chart?

Face the card so the light source is directly shining against it so no shadow is cast.

Then place the test tube against the card on the white surface next to the colour line you are checking.

I think it does say in the instructions somewhere and this is how I have been testing it.

Kind Regards,

Adam

 

[BigIan]

Face the card so the light source is directly shining against it so no shadow is cast.

Then place the test tube against the card on the white surface next to the colour line you are checking.

I think it does say in the instructions somewhere and this is how I have been testing it.

Kind Regards,

Adam

yep thats the way i do it, it never turns out exactly to match the colours its just a guide..

 

[curlyriff]

I forgot to mention that natural light is best.

Kind Regards,

Adam

 

[Gvilleguy]

I have done about 100 tests using the API kit, and I find that putting the glass directly against the card darkens it as frogmarch said, due to shadowing. I instead hover it about 2 cm away from the card with a light directly behind my head. This seems to give me better results for matching the exact color of the water.

 

[curlyriff]

I have done about 100 tests using the API kit, and I find that putting the glass directly against the card darkens it as frogmarch said, due to shadowing. I instead hover it about 2 cm away from the card with a light directly behind my head. This seems to give me better results for matching the exact color of the water.

It shouldn't create any shadow behind the tube if you have the light source direct as it will pass through the colour and reflect the light back of the white card.

If you place it further away it will create a lighter colour than actually rshowing. It is written somewhere in the first few pages of the instructions as I have read them.

Although you are holding it against the card a couple of mm gap would be sufficiant for the light rather than 2cm.

If you test with it toofar from hthe card then you will show different shades as light relects differently over different distances.

I would not worry too much anyways as has been mentioned it is only an estimate and guidline, you are ore than liekly slightly to what you think as human eyes are not best t reading colour variations anywyas and for men who are all slightly colour blind in mainly greens and blues it can be even harder.

Every person will see it slightly different so I wouldn't worry about it being 100%

Kind Regards,

Adam

 

[waterdrop]

I agree with the light behind the head, and against the card or 2mm away should'nt matter much either way assuming your whole light, head, tube, card are all relatively close. I used a 60 watt incandescent in a spot focus type fixture. We've had discussions in the past about not using compact fluorescents as so many of those give off a green-yellow cast and make the green darker than the incandescents do.

But as I'm sure GVG and anyone else who's done it a lot will agree, the most important things are the "trends" and the reading of your logs over many days and weeks, not any given one reading.. once you get the hang of that you realize that its more of a something/nothing thing rather than judging shades so much.

~~waterdrop~~

 

[frogmarch1987]

thanks for the advice everyone. At least I know not to worry too much about getting the exact colour

 

[OldMan47]

A others have already said, I stand with my back to the light source, which is often sunlight through a window. I then hold the glass tube against the white area of the card and use the lighter color that shows up in the middle of that tube as the thing I compare to the colors on the card. If I see a similar color hue, not intensity, I choose that as my reading. I use hue rather than color intensity because the lightness / darkness of a sample too often misleads me to read the wrong value. The hue, on the other hand, seems to give me consistent results from my testing.