Decide first what features you want...a cord is nice so you don't have to bend over all the time (not such a big deal if you only have one res) figure out what's best suited and look around for the price you can usually haggle with a hydro store owner too if you add like 10 to 20 percent from the cheapest online price so if ya see it online for 100 offer 120ish it's worth a shot

rhizome brought up a good point about having a replaceable electrode

I went with a 4 in 1 hanna pen tester that auto adjusts for temp difference I think mine was 150ish at the store but I've seen it online for just over 100...

I calibrated it once and haven't had to do anything else since

As far as accuracy it's noted to .05 ph and 2% variance on ppm I'm pretty sure it's right on point too cause even if I test several different res's it still lands on the exact same number it chose before for each res...oldsanclem has a point that you want repeatable I'd say that's about the most important of all cause if you dip it in the same solution and it changes it's answer well that's not so good haha...as long as it's within .1ph and 5% on ppm I'm sure you'll be fine regardless of brand

gl let us know what ya go with :thumbsup: