I have used their DKH test kit and its fine
Agreed, here are some numbers I posted on the BAR forum a little while back
"Went crazy with the Alk. test kits today. Normally I'm sick of drops in vials at the end of the day, today I was motivated here you go...
Alk in my tank according to our precious test kits
API-> 9dKH (brand new)
Hagen-> 10dKH
SeaChem-> 6.7dKH
Salifert #1 -> 9dKH (one step type with orange/red tritrant)
Salifert #2 -> 7.4dKH (two step less than 6 mos. old)
Salifert #3 -> 6.7dKH (about one year old lives in my apt. with no light and stable temp, two step)
Here's the kicker, chem people help me out->
One step Alk test (Salifert w/ Salifert reference solution)
Salifert #1 -> 5.8dKH reference solution is supposed to be 7.0dKH
Strange huh? I kept hearing Flava Flav "You can't trust it" playing in the back of my mind."
"Did some more tests this morning using the salifert reference solution and am now ready to give up testing Alk
Salifert #1 gave me 9dKH from my tank, & 5.8dKH using the 7.0 reference solution (repeated twice)
API gave me 9dKH from my tank, and 7dKH from the reference solution
Hagen gave 10dKH from my tank, and 8dKH from reference solution
I think my tank is around 9dKH, right where I like it. I think...."