Salifert test kit (calcium)

[Captainhemo]

I was told that even though Salifert test kits appear to have the "resolution" to be very accurate, it isn't uncommon to do 3 tests in a row and get 3 different results.
Elos kits on the other hand don't seem to have as much "resolution" but at least the tests come out the same each time when testing the same water sample