In hydro it sure as shit matters.
I use a Greenlee tester and it's range only goes up to 2000, so I don't even know of a meter that ranges that high, but I'll bet my ass that if you run ANY plant at 4000 PPM for 2 weeks, they will be fucking toast.
https://www.rollitup.org/t/call-it-hydro-exp-gone-mad-imput-wellcome-autoflowering-strain-gone-nutz.764237/
the only trouble was it grew into the light hence the bleached tops on 2 of the colas ......notes and pics
ppm can be high as u want if u account for the PHing and water replacement .......by the end of it i was doing a gallon a day and 6 PHing
i repeated the experiment 3 times so far (most likely will again once build a RDWC with res)
that was the first time (blue mammoth)
the 2nd the water was way to hot for too long cooked the root mass to shit ....so i killed it off would never have the time to build mass (thc bomb)
3rd the plant hermied but i have had trouble with that strain pushing it to long ....but the yield was still way over what strain called for ....think it was 17 oz with 16 sellable last was to fluffy (narcotherapy)
yes i am insane and have crazy ideas but i done the leg work to know the shit i am talking about ......i like to work with auto flowers since they react so much faster then photos i can actually judge what works and what does not .....i have applied the skills i learned from that on here and my own grow in OR .....i know what i am doing
in hydro the only things that matters
1 water temp.... 65f
2 PH 5.8
if u want to know the best mix of feed products i can tell u ........and this was all because i made a mistake and did drain to waste at the start of life and tho the first 2 weeks ....then i started going off track