Confused about reading my pH strips

[qbert]

Hi. I've got my first ever batch of babies going. Frankly, it hasn't been going well; I've had more problems than I can count.


pH'ing my water has been particularly puzzling.

I use these pH test strips. At first I was using tap water, and now I use RO water from the store, and I get the same results.

If I dip the strip in plain water, the pad never changes color - it stays bright yellow (which on the legend is the lowest end of the scale: 4.5).

This is the first thing that confuses me. Plain water (especially RO water) should be 7.

So I figure maybe the strip can't read plain water exactly. And I'll add some pH Down. But when I test it again its still bright yellow.

Basically, every time I need to add a fair amount of pH Up to get the strip to read 6.25-6.75 (soil grow, mix of Fox Farms Ocean Forrest & Light Warrior with added chunky Perlite and soil sweetener - dolomite lime that is).

I'm using Earth Juice Natural pH Up and it takes about 1/2 - 1 teaspoon of pH Up to get a full gallon of water to about 6.5.

I really don't understand why I have to add pH Up to get plain water to 6.5.

Can anyone explain to me what I'm missing?

Thank you.

 

[Japanfreakier]

The link is for testing your urine's pH. Maybe get some at the pet store?

 

[Nicoli]

Get a digital meter already.

 

[qbert]

The link is for testing your urine's pH. Maybe get some at the pet store?

I assumed it wouldn't matter, that it would work fine for water. But I could've been wrong. Ones for fishtanks then?

Get a digital meter already.

I thought about it when buying equipment but decided against it. Figured strips would be simpler. Can't really afford to up an order one today, either. Recommend any in particular?

 

[Japanfreakier]

I would assume the same thing and it doesn't make much sense to me, but if your water was that low you wouldn't be able to drink it. Most tap water in the U.S. as you mentioned is neutral. So even though it doesn't make any sense that the strips wouldn't work I'd go for different ones.

 

[professordank]

I'd stick with dedicated horticultural pH testing equipment. I definitely prefer the liquid tester to litmus paper.

 

[FreezerBoy]

You may have bum strips. Liquid is liquid. BUT, if the strip is at it's lowest reading, adding pH down won't change the reading as it's already low as it can go. What happens when you add baking soda?

I had the phion two color strips. The second color proved to be useless and the strips were off by 0.5 compared to my aquarium test drop kit. I trust the aquarium drops above all others as they kept my marine tank thriving for years, a far more sensitive environment than weed.

Digital pH testers are a crapshoot and little more than toys. If you have several tubs to manage, they can be very useful. For a single tub, drops are faster, easier and more trust worthy.

 

[qbert]

Ok, I think I figured it out.

Stopped by the local hydro store on the way home from work and got a little bottle of the liquid tester.

Annnd ... the strips were fubar. Either unusable in this application or just plain junk.


For the record, the RO water measures ~5.5, but it only takes the tiniest, tiniest bit of pH Up to adjust it. I'm surprised the plants are alive. The amount of pH up I put in .. whew .. must've been at 13. And then jolt down to 5.5. No wonder they were going crazy.


I also bit the bullet and ordered an Oakton Waterproof EcoTestr pH 2. A while back I thought about ordering a Blue Lab, but the replacement probes for the nicer meters are as much as a new Oakton pH2. Whether I prefer it or the drops I'll have to see. The drops may be quicker depending how often I calibrate the Oakton, and I'd trust the results from the drops more than the meter.


Now I'm wondering what to do.

The plants are in rough shape. Brown spotting, curling and twisting, yellow edges, whole yellow leaves, stunted growth. I just watered them on Saturday night with plain RO and when I took cuts Sunday they were turning bad fast. After cuts I gave them badly pH'd water (probably super high), and the dirt is still saturated right now.

They're in 6x6 black square pots, but I just grabbed some taller 6x6 white pots. My cab is a little warm so I'm thinking its worth re-potting them. But maybe I'm better off just leaving them where they're at for now? As soon as I can turn them around a bit I want them to go under 12/12.

Then I'm thinking flush with pH'd RO water with Clearex? Would I want to still add CalMag to that or leave it out for the flush?

Then after the flush some light veg nutes.

Any advice on the recovery plan?

 

[Japanfreakier]

Depends on your soil. If your soil is inert I'd flush it then feed them correctly. If your soil is organic then just flush them. Wouldn't do much else than that.