I have used Salifert, Elos, Redsea and a bunch of others. While it's really hard to guage the accuracy of all these kits, one can assume at least +/- 10% readings. With the API kit I see small enough changes reflected in the readings to give me confidence that it's within the ball Park of ELOS and Salifert, so at a the current price API is a clear winner. I also like that these tests are simpler to preform than most of the others, so thats a real plus.
Rating:
[5 of 5 Stars!]