Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Is it a problem that the colors on the card are hard to tell apart?
Sometimes you get faulty cards, where the colors are printed wrong. Go online to API or google images and see if your card matches what you see on your monitor (or pretty close)
If it is a problem with the method not showing different colors in the test tube:
Shake the bottles of reagent REALLY WELL. I shake all of them if it has been a while since I have used them, and the ones that instruct you to shake get shaken even better.
Hold the test tube against a soft white background with really good light. Be careful of other colors in the room. For example, one test turns a subtle green. I hold the test tubes near a window for good light, but they pick up some green from the trees, so that test when I am looking for green cannot be read near a window.
And last, do a 50% water change, then test again. Depends on what you are testing and what is in the refill water, but that will often reduce toxins, no matter what they were.
If it is a problem with your water here is a way to see a slightly different color:
Use only half the amount of tank water, but the full dose of reagent(s). Then divide the answer by 2.
Use half tank water + half RO or distilled. Then multiply the answer by 2.