I have an Apera, flawless operation and accuracy for the past year, I calibrated it once but check it against reference solutions occasionally. I would get a bluelab next though. I always have a PH kit around just in case though, so be sure to get one of those no matter what probe you get. Make sure you have the 4/7 ph reference solutions to calibrate it, and most importantly, you need KCL storage solution. Keep that tip marinating in KCL whenever you aren't using it. One tip about the PH kits I learned from my aquarium days, if you have trouble figuring out which yellow or green you are looking at with the hydrofarm kit, get yourself a SERA freshwater PH kit-it's a couple of dollars more, but your paying for German accuracy and extremely easy to identify PH colors. The cheap PH pens aren't worth it, if that's all you can afford get the PH kit instead.