short and sweet -
so, are you using it out of OCD or is it needed? if you will evolve into less testing as you are more familiar, definitely go with strips. if you have to test all teh time, the ph pen/probe is a good idea.
more reasoning added...
you are better off with a cheap 100 pack of 1/2 pH resolution strips. (pH resolved by 0,5 with 4 colors for easy reading)
the pens are nice. if you are going to test multiple things per day or just daily use, it may be worth it. with good products and a good SOP you don't need to test so often.
7usd for a 100pack that has lasted me 2-3 years and i still have 60-70 strips remaining. i have a well-buffered nutrient brand. my pH doesn't swing/drift. i used to test more often but it is not needed with good fertilizer brands. If you keep rez dark and relatively cool, you only need to spot check occasionally. At this point i use 3-5 strips per year. i'll spot check before germinating any expensive seeds, for example. but the 1000 or so i made, meh. lol. learned the hard way when i pissed 160 usd down he tubes bc my tap water pH shifted from 8,4 to 7,0 and i was not adding fertilizer so i had to add some acid to adust the assumed 8,4. ended up too acidic and 8 of 10 seeds died. 20 usd per seed... makes you think twice about being lazy.
as far as the rez, i just have a regular maintenance and rarely test pH - just enough to avoid any issues. i don't even clean my rez that often. maybe 1 time during a grow but i've also gone an entire grow without scrubbing it down. my point is i'm a bit sloppy and i still don't have ph issues. This is an easy thing to avoid with some good choices of fertilizers used. if pH drift is occuring it is more likely the fault of the product than some external force.
maintenance - you have to re-callibrate a pen. which means you have to buy and store stock solutions of specific pH. some are 2-point, some are 3-point callibrations. you need a solution to store the probe in to extend its life. you don't want to spend 50-150usd and then treat it liek shit and get fewer years out of it. the point is it seems easier on surface to test stuff, which it is, but there's a ton of maintenance and special needs that make you spent a lot more effort on a pen than strips.
soil has it's own impacts on pH too. gives you a little leeway on it, typically. slightly self-correcting
so, are you using it out of OCD or is it needed? if you will evolve into less testing as you are more familiar, definitely go with strips. if you have to test all teh time, the ph pen/probe is a good idea. (pasted to top)
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