Red Sea Foundation Pro Test Kit Coral Reef Aquarium Reliability

I was using a 10 year old test kit which was giving lower result specially Ca and Mg. I bought a new test kit and I think the results are higher. Below are the numbers a day apart

Alk Ca Mg

New Test Kit 9.2 450 1550

Old test kit (Next day) 8 .4 410 1220

I tested the water at LFS using salifert test kit and the numbers were 40 ppm lower in Ca when Red Sea was reading 490 ppm. I didn't test Mg at LFS which I should have.

Has anyone using red sea test kit thought their numbers were too high? I am dosing Ca and Alk but can't explain my Mg numbers since I don't even dose Mg. When I opened the solution of the new test kit, some plastic like substance did fell down which I thought was from the cap but shouldn't make a difference.
 
The older kits might be reading lower because water has evaporated from the titration agents. That seems to be fairly common. I would trust the newer kits.

For hobbyist test kits, a difference of 40 ppm in the calcium results isn't that bad. Is the Red Sea a drop-counting kit? If so, what is the ppm per drop?
 
The older kits might be reading lower because water has evaporated from the titration agents. That seems to be fairly common. I would trust the newer kits.

For hobbyist test kits, a difference of 40 ppm in the calcium results isn't that bad. Is the Red Sea a drop-counting kit? If so, what is the ppm per drop?

Yeah it's basically a drop count kit. 1 drop =.01 ml = 5 ppm Ca and 20 ppm Mg. I trust the newer kit but high Mg is kinda throwing me off. It's almost off the chart and I am not even dosing it.
 
Hmm, well, I would hope for a bit closer than 40 ppm, but not that much closer. What brand of salt are you using? 1550 ppm seems higher than most.
 
I was using Reef Crystal's for a long time but switched to red sea coral pro since last water change, changing 30 gal every 4 weeks in a 180 gal. I was using Bionic 2 part until 6 weeks ago which adds some magnesium but that can't explain the number.
 
I think Red Sea Coral Pro should be about 1400 ppm according to their web site. I might try mixing up the dry salt a bit, if that's easy, to see whether that helps.
 
I think Red Sea Coral Pro should be about 1400 ppm according to their web site. I might try mixing up the dry salt a bit, if that's easy, to see whether that helps.

Red sea have this feature called Mybatch where they give you the numbers for that batch of salt. It says 1396 for Mg. When I measured it last I got 1480.
 
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