Help matching test-tube color with nitrate test card

[vfc]

I don't know about you folks, but I have a hard time trying to match my test tube color with the API Nitrate color chart.

For starters, the color scale is not linearly progressive; 0 to 40 is easy, 80 looks like a lighter shade of red than 40, and then there is the big jump to 160.

Next, I can't find a consistent way to illuminate the test card and test tube to accurately match up the color. Seems like my incandescent lights don't produce a strong enough light to shine through the liquid. So the water mix looks darker and gives a higher nitrate reading. When I hold the test tube and card by a window, the sunlight makes the readings much lower.

I also get a closer match to a card color if I stand the tube on end. When I lay the test tube flat on the card, I rarely find a color that matches.

I wish I had a nitrate level between 5 and 10; then this won't be an issue. Unfortunately, my nitrates are usually over 40.

Any tricks or secrets to measure high nitrate levels using the API test kit?

 

[salsa]

Waterchange then try again?

 

[vfc]

The tanks have been set up for a couple years. I have bought two API kits and I still can't accurately measure nitrates 40 and higher.

 

[pdbrady]

You can't hold the tube to the card and get an accurate reading. The problem with reading these is the shadows cast in the various positions. If you stand the tube on end, it appears darker, as with holding it to the card. I hold the tube up in front of a light, and hold the card out next to it, but out of the light so it doesn't shine through it.

 

[dmopar74]

You can't hold the tube to the card and get an accurate reading. The problem with reading these is the shadows cast in the various positions. If you stand the tube on end, it appears darker, as with holding it to the card. I hold the tube up in front of a light, and hold the card out next to it, but out of the light so it doesn't shine through it.

the directions say to hold the tube against the card, even if it is darker, its the correct way of doing it. im shure the people(scientists?) that designed the test kit put that in the directions for a reason. holding it in the light will produce a lighter color, which is nice because it shows lower nitrates, but innacurate.

heres a quote directly out of the api freshwater master test kit booklet-"step 8. The tube should be viewed against the white area beside the color chart. Color comparisons are best made in a well lit area. The closest match indicates the ppm(mg/l) of nitrate in the water sample."

i also have a hard time determining the closest color sometimes, so i also ask my wife which olor is closest and average it out. but holding it in the light or not against the card will "magically" lower your nitrates 20ppm or more.

 

[banjocat]

I also like how it has warnings about getting the chemicals on your skin, but with this test it is almost impossible(with all of the steps) to get nothing on your hands(unless you wear rubber gloves each time). I'm talking about after the chems have been mixed with the water by the way. The ammonia and nitrite don't involve as many steps. I guess the steps are necessary for this kind of test and can't be avoided.

 

[gomezladdams]

I have no ability to discern the colors.I mix the solution then hand the tube and card to my wife that has an art background

 

[ITHURTZ]

I just hold it up and judge. If it looks yellow 5, orange 10, dark orange 15-20. Red water change time! I find it real easy to read the nitrate, ammonia is a different story. Mine only gets to 30 on weekends. I do 3 massive water changes a week so I dont really care to check it since I get knocked down to 5-7 when I am done

 

[vfc]

Problem I have is that I have 15PPMs of nitrate out of the tap (15 I can read on the test card). I also have .5PPMs ammonia out of the tap; so when that goes in the tank, it gets converted to nitrates in a short time. I also have chloramine; Prime breaks it into chlorine and ammonia. That ammonia gets converted into nitrates. I would guess that if I took all my fish out of the tank and did a 100% water change, I would have ~25PPMs of nitrates in a few hours just from the tap water alone.

So given my water source, I end up with a high nitrate count on all my African Cichlid tanks that are stocked on the high side to minimize aggression. I'm doing weekly 50% WCs, but I don't want to increase that if I don't have too because of the amount of time and effort it takes with large tanks. I wish I could accurately tell the difference between 50 and 100PPMs.

 

[OscarRobinson]

Try being color blind and trying to read the cards. Nothing like asking your 7 year old daughter to read the card for you. Any way what I found that helps read the tube is to put a very white index card behind the tube and then hold it against the color card. Seems to help a little. And by the way I was a printer for about ten years and those color cards have a certain degree of inaccuracy(sp?), they also fade over time and only have a 1 year life span.