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Old 08-28-2013, 12:24 AM   #1
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Why are test kits so different?

I'm guessing this has been covered but why do they vary so much? I went and bought what I thought was a good kit in Red Sea. I bought their master kit or whatever they are called. I test it about once a week and for example my AK was testing between 9.2-9.8. I've been having bleaching and receding issues with some of my LPS. I initially assumed it was too much light. I lowered the intensity and duration. They still weren't getting any better. I brought my water samples down to the Elos store here in NJ and they tested my AK in both tanks at 6 and 7! That's way low. I thought maybe I goofed, so I came back home and tested each tank twice more with the Red Sea kit. Same results. That's a big swing between the two different tests.
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Old 08-28-2013, 01:51 AM   #2
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That's an awfully big swing. Have either your Red Sea or your LFS test kits expired? I use the Red Sea kit myself and bring in water samples once every 3 months to my LFS that uses ELOS kits. They're always very close to each other.
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Old 08-28-2013, 09:33 AM   #3
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Test kits can go "bad". The reagents break down over time. There should be either a lot number, or an encoded expiration date on your kit. Check that (you may have to contact Red Sea if it's encoded somehow), and see if your kit is past its prime.
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Old 08-28-2013, 02:27 PM   #4
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My expiration date says 5/15. I just again tested it with the Red Sea - 9.4. Elos - 6.5. WTF!
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Old 08-28-2013, 02:30 PM   #5
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I have found that there are 2 different scales when measuring Alk (KH). The most common seems to be 1 drop = 1dKH. My other test uses 1 drop = .5meq/l. The conversion is 1 meq/l = 2.8dKH.

So using the conversion factor of 1 drop is either 1dKH OR 1.4dKH and assuming the wrong conversion was used, 9.2dKH would correct to 6.5dKH and 9.8 would correct to 7dKH. I think there may have been a calculation error.
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Old 08-28-2013, 02:32 PM   #6
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Hmmm.. Maybe you're on to something
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Old 08-28-2013, 02:34 PM   #7
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And as a follow up, I have 2 different test kits (one cheaper than the other) and they both use 7 drops to titrate. One is scaled at 1 drop for 1dKH and the other is 1 drop per .5meq/l (or 1.4dKH). So one test says my dKH is 7 while the other test says 9.8dKH or 3.5meq/l.
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Old 08-28-2013, 02:47 PM   #8
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Well not saying its the Red Sea test but had the same problem and was using Red Sea. But my problem was with the mag test it was telling me that my mag was 1400 and over but was losing some of my sps went and got a elos test and it told me mag was at 1100 crazy. Tested like a mad man with both test and the Red Sea was still saying 1400 and above elos 1100. So now I use elos for mag,cal and alk.
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Old 08-28-2013, 02:48 PM   #9
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Actually, that also was my issue. My MAG said 1500 and Elos said 1250. CA was 450 with the red sea and 325 with Elos. It's just crazy to see the differences.
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Old 08-28-2013, 02:49 PM   #10
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These are the directions for the RedSea, looks like the conversion needs to be done that was mentioned above:
Quote:
Directions for KH Alkalinity Pro Test Kit
1. Using the large syringe provided, place exactly 10 ml of the water to be tested into
the glass vial.
2. Screw the glass vial onto the bottom of the Titrator.
3. Ensure that the dispensing tip is on the 1 ml titration syringe and fill with 1ml of
Alkalinity Pro Titrant. [see note for filling titration syringe.]
4. Insert the syringe into the center of the Titrator so that the volumetric scale on the
side of the syringe is visible. The graduations of the volumetric scale are 0.01 ml,
equivalent to an alkalinity of 0 .05 meq/L (0.14 dKH).
5. Add the first 0.4 ml of titrant (equivalent to an alkalinity of 2.0 meq/L Ė 5.6 dKH) by
pressing the plunger of the syringe while gently swirling the Titrator. The test sample
will obtain the titration start color as shown on the instruction card after the first few
drops of titrant are added. Continue adding the titrant gradually, swirling the Titrator
after each addition and paying attention to the color in the vial. As the color in the
vial approaches the end color as shown on the instruction card, add one drop at a
time, swirling after each drop, until the end color is achieved.
Note: If you have added 1 ml of alkalinity titrant, without reaching the end color, the
alkalinity of your water sample is more than 5 meq/L (14 dKH). Refill the syringe and
continue to add titrant until you reach the end color.
6. Note the amount of titrant used (according to the initial and final position of the
plunger not the liquid surface) and use the table on the instruction card to calculate
the level of alkalinity in the water sample.
7. Dispose of any unused quantity of titrant.
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