Ppm wtf.

anyone have an idea. Just got a ppm meter. Lost a whole garden. Think it was salty cococoir. Out of the bag, ran 20ppm r.o. water. Runoff 800ppm. Went and got brand new bag of promix hp mycorrhizae. 20ppm in 1200ppm runoff. Make any sense?

Easy fix; Don't messure runoff. Just worry about the PPMs you can control. The input ppm

I thought potting soils clean. At some point high ppms are bad?. Over nute etc.?

What kinda pen did you get? What conversion does it use? What are/were you feeding them?

I have never heard of coco being so salty it killed plants. I run the cheapest coco you can buy, and even that is fine. I don't rinse or buffer mine. I just plant in it and give a good run-off watering the first water after transplant. I water everyday with minimal runoff. As long as my root zone stays semi saturated it curves the salt buildup that you hear talked about. But thats me. Nothing more than my opinion.

Vivosun meter. Soils out of the bag new. Transplanting into it.

Okay, But pro-mix isn't soil(unless they have a soil I am not aware of)
And promix isn't coco. 2 different animals. I suggest you do a search for pro-mix vs soil vs coco

I've grown with a few different brands of coco. The two best brands I've used are Tupur from Royal Gold, and Canna Coco. Those are the only two I'll use straight out of the bag without rinsing. Everything else I've had to drench with water before using to avoid issues.

The coco could have been pre buffered, the pro mix definitely was with at least lime....
Pushing RO water through a buffered media should have resulted in a runoff ppm increase.

I've seen it go the other way around. 250+ ppm tap water, through clean coco, getting lower runoff readings.

Cation exchange capacity.

I buy a known good quality coco coir (canna) and I never measure run off. I pH only my reservoir. I keep that 5.5 to 6.0 and somehow my plants survive.

Promix HP has lime and starter fertilizer in it. The coco could have had too much salt, but watering to runoff when planting in it should be good enough.

How exactly did you "lose" your garden? What did you give them besides RO water? Those ppm numbers you stated are high, but shouldn't have killed anything so long as you got some runoff when you planted. When I start in promix hp I water to runoff with plain water @ around 0.4ec and ph around 6.0. Starting in coco I just use 1/2 dose of the feed the big plants get and water until just barely getting runoff. Don't ever start anything in coco without adding some food. I use canna coco now, but really everything I've tried is pretty much the same just feed light to runoff first watering and it's good to go.