Review on Accurate Temperature Spurtar for Aquariums with 0-9999ppm by Hector Liamsi

Just arrived in the post (quickly too) Just read the instructions and calibrate. another pin I almost sent back. Some of the newer and more expensive digital pens can be difficult to use, if not then there is already some kind of glitch. unless you pay more than a hundred dollars. I keep buying these $13-$20 pens knowing they will be recalibrated when they arrive. I usually use about three to four per plant. I also always measure the pH with two pens to make sure the measurements don't go crazy. Then a backup that I know is always on hand, especially when growing, you can't have a pH level in your plants that they don't like.