I compared the results I got using 3 different calcium test kits. I used a Lamotte, a Salifert and a Sera. I only did each test 1 time and followed each set of instructions the best I could.
LaMotte
Cost: aprox $40
Made in USA
It measures in increments of 10
ppm, has nice glass parts and easy to follow instructions. But, it's hard to tell when you reach the end color and you need to dilute the tank sample with distilled water (I used 0
TDS RO/
DI water for the test). Also, the plunger it somewhat tricky to read. It goes up to 200 in increments of 4. If the plunger reads 80, your at 413
ppm, if 82 your 423, if 84 your 433, etc.
My result: 433
ppm
Salifert
Cost: aprox $25
Made in Holland
It measures in increments of 10
ppm, it's easy to tell when you reached the end color and it has easy to follow instructions.
My result: 430
ppm
Sera
Cost: aprox $12
Made in Germany
It measures in increments of 20
ppm and it's hard to tell when you reach the end color.
My result: 440
ppm
I think Salifert is the easiest to use. I bought the LaMotte kit in 1991, used all the reagents and put it away. I just ordered refills ($16) to test it out. Once I use up these reagents (50 tests), it's getting put away again..lol. The Sera kit is OK for a quick, cheap test.