do you still need to callibrate a TDS meter then? when you buy them do they come callibrated?
i do have a ph pen the cheap yellow ones on ebay but i never seemed to have much luck using it on my old shrimp tank as it never stayed stable it kept rising as the water moved round? i did callibrate it but in the end gave up
do you need to store them in a liquid as i also read that if you dont store them in a liquid then they stop working anyway?
im about to buy an R/O machine and guess a TDS meter would be needed really but not checked as i have been buying my RO in
sorry to hijack