Ruben's Reef
Ruben's Reef
I also use Hanna Checkers for my test but something I find out recently with an unacurate reading is that when it show C1 and you put the vial in, it should blink 4 times before changing to C2. If is blinking more than 4 times then you need to clean the vial properly and try again, otherwise will throw your reading results off.
