Red Sea Reef Foundation Test Kit - Old and New Kits have different readings

[RockStacker]

Has anyone run into this before?
I have been using the Red Sea Reef Foundation test kit for many months now. I'm about to run out of reagents so I bought a new kit.
I then tested my water using the two different kits to see if they provide similar readings (they should, right?)

My tank parameters:
Water temperature: 80F
Specific Gravity: 1.025
pH: 8.2

Below is what I got with the test kits:

Lot# 162 (old)
Alkalinity = 7.7 dKH
Calcium = 400ppm
Magnesium = 1420 ppm

Lot# 293 (new)
Alkalinity = 8.8 dKH
Calcium = Over 500ppm (I used up 1ml of the titration reagent and the test sample had not yet reached the end point color)
Magnesium = over 1600ppm (I used up 1 ml of the titration reagent and the test sample had not yet reached the end point color)

Now I am not sure if my new kit is bad, or if my old kit was bad all along.

I am leaning towards the new kit being bad because those Ca and Mg readings are way too high considering what I dose.

 

[daugherty]

that's a big problem with test kits. many new and old are really not that accurate. they have done lab grade testing and use different test kits. old new and expired kits. some of the expired kits had closer results then some of the brand new kits.

 

[Banana Man]

Have you tried to run a test with the same kit twice and see if you get the same result? It's probably unlikely but maybe the technique you use is causing a problem. I often wondered how accurate those tests were. I'll have to test mine out as well

 

[RockStacker]

Have you tried to run a test with the same kit twice and see if you get the same result? It's probably unlikely but maybe the technique you use is causing a problem. I often wondered how accurate those tests were. I'll have to test mine out as well

Yeah I have run at least three tests on old and new kit.
Both kits had consistent results. The new kit always registered higher values (too high) compared to the old kit.

I got a response from Red Sea about the calcium test. The lot# I had for the Calcium-B reagent (lot# 2103) is recalled and they will send me a replacement.
So this explains the calcium issues, but still not sure what is going on with the alkalinity and magnesium.

I have a separate Red Sea alkalinity test kit that I keep as a backup, this one only has a resolution of 1dKH so not very precise.
However, this test still shows that my tank's alkalinity is between 7dkH and 8dKH.
My old test kit falls within this range, and the new test kit goes over this range.

Now a difference of 1dKH might not be catastrophic (specially when taking 7.7dKH vs 8.8dKH - both are good values in my opinion), but I would like to have my test kits at least be in the neighborhood of what the actual values are.
Test results that are off-target could have me chasing the wrong things and make bad adjustments as I find tune my dosing regimen.

And the 1600ppm+ magnesium, I'm still not sure how my tank can even get that high - unless I have fish that poop magnesium pellets.

 

[Civicdemon]

Use the same suringe to pore the water into the little glass containers, I think the new one is slightly bigger than the old and put in more water. I Had the same results and when I used the same suringe I got better results closer toghether.

 

[daugherty]

something for everyone to read.

http://www.advancedaquarist.com/2012/6/chemistry

 

[RockStacker]

Use the same suringe to pore the water into the little glass containers, I think the new one is slightly bigger than the old and put in more water. I Had the same results and when I used the same suringe I got better results closer toghether.

I compared all the volumes of the different syringes on the two kits. They all match up. 1ml on one is 1ml on the others, 2ml = 2ml, etc.
I think you may have a defective syringe or a mismarked one in your kit.

 

[RockStacker]

The Calcium Reagent B is confirmed bad, so Red Sea will be sending me a replacement. So that addresses that issue.

I got a response from Red Sea regarding the alkalinity and magnesium tests.
They recommended the following:
1. Mix a small batch of new saltwater to 1.025-1.026 specific gravity.
2. Check the manufacturer's advertised parameters for Magnesium and Alkalinity.

This should give me a reasonably close control sample to verify my new test kit.
Assuming I make the water right, there would be expected variances but a good kit should be within 50ppm on magnesium and within 0.5dKH on alkalinity.

If the new test kit's results are in line with the new saltwater's expected levels, then the new test kit (at least for Alk and Mg) are good. And most likely my old test kit has gone bad over time.
If the readings are still way off on the control sample, then they would like me to tell them about it and will go from there.

I understand that user error is always a factor, but a 1.1dKH swing on their titration test would take more than an honest user error.
And a 200ppm+ swing on the Magnesium test... that would be like trying to do a titration test after taking 6 triple shot espressos.

 

[steveh]

Please also refer to the instructional videos on www.redseafish.com which show how to use the tests. They are very precise tests and even experienced hobbyists benefit from watching the short instructional videos.
Because Red Sea cannot monitor every forum, it is always best to go to the Red Sea website and contact the company directly, through the enquiry form.