Slurry testing questions

Hello All:
I read Roberts tutorial on soil pH/tds testing and have a few questions.
1. Walmart online has a variety of meters, any recommendations?
2. The tutorial says to use distilled water. My well water runs 7.0 pH and is very
hard.I used pH down to bring it to 6.5 and in past grows used this water
exclusively. Is this wrong, and should I use the filtered water from the walmart
machine not only for the slurry test, but also the whole grow?
3. I’m using 10g fabric pots and wonder how to gather samples at the roots as
recommended. Thanks and Happy Trails .

How have your growing results been?
That’s the important thing.

All I used is a Brita water filter on my tap water. I filled a 5 gallon bucket with straight tap water and another 5 gallon bucket with filtered water.

The filtered look clear like water should. Now the unfiltered water was actually brown color. No, I’m not joking. And it is also chlorine to death. Just nasty.

I have never done a PH reading and my grows get better and better as I get more growing sessions in aka new plants to full bud. Rinse and repeat.

My last 2 grows(indoor) were a disaster. I’ve identified/corrected some issues,but thought it best to go back to basics. I’ve been a successful outdoor grower but am trying indoor. My problems stemmed from becoming root bound, which caused a host of issues, the fabric pots ought to correct that.

Water is an important part of growing inside. Knowing whats in it helps.
Do you have a TDS meter? (Total Dissolved Solids)
Im curious just how hard the water is. Calcium is vital and walmart filtered water may lack in that regard. It can be added tho as many of us do.
Fabric pots are great. minimum 3 gal for autos and 5 for photo period types.
What kind of soil are you using?

TDS meter no,I’m looking for recommendations and cost is relevant. I’m starting the seedlings in a plain, unadulterated potting soil. I’ll be using FFOF as the primary medium. I like to stage in progressively larger containers, increasing the ratio of FFOF/potting soil until I park the girls in the 10g fabric pots where 100% of medium will be FFOF.
My well water is hard ppm unknown. I do know it varies depending on the amount of rainfall we receive. I did religiously pH test my water prior to watering, and monitored the run-off also.I’m trying Blue Cheese this time around as the strain is better suited to my grow set-up and experience level.
Does pH down effect the calcium content of my water? I had issues with deficiencies,but not knowing how the root bound condition affected the overall grow, it’s hard to say if this was the driving factor on the last 2 poor grows

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My wife has a Brita and I ran some tap water through, testing the TDS before and after. It did not do much. (550 ppm to 450). I ran into all kinds of issues and solved them when I bought a portable R/O unit:

As to the slurry test it’s important to use distilled water and don’t PH it beforehand. Also; a slurry test supplies data on the salts present and a TDS meter along with a PH meter is very important.

There are many cheap meters that do fine:

A PH meter is absolutely essential. I recommend this one:

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You must use distilled or ro for the slurry test, otherwise your result will be very inaccurate. Distilled and RO water basically have nothing in them but water, so when used for slurry tests they won’t affect your test results.

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Thank You. I was using probe type meters which gave different readings,but now use Jellas test strips.We used them in chemistry class ages ago, hopefully they are accurate.
I see the reasoning for using the distilled H2O for the slurry test… This will enable me to amend the soil pH…correct? I’m confused though that when I use the well water,won’t that change the soils make-up?

How many transplantings are we talking about?

Single plant grow in a 3x3 tent using ViperSpectra 600w LED. I haven’t heard yet as to how soil samples are collected for testing (2x monthly) per the soil test tutorial. Eventhough thats a ways off, I’d like to be familiar with the process. Thanks for bottle feeding me.

When you water your plants or feed them, that changes the pH and ppms of your medium. To test the pH and ppms of your medium, you can do one of two things:

  1. Test your run-off
  2. Slurry test your soil.

Run-off testing helps you see whether what you’ve just put into your medium is too much, not enough, or just right.

Slurry testing is a way to get a baseline reading, w/o adding anything, of your medium’s pH/ppms. The slurry test is more indicative of long term issues, since it’s not testing only one particular feed/watering, but rather the medium, itself.


Got it. But just to be sure, The slurry test shows me where to adjust the soil if needed. If my intake/run-off water is also pH correct, then there shouldn’t be any issues with soil chemistry as the grow progresses.

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The pH and ppms can change quickly; they need to be monitored often.

But yes, if your run-off comes out looking good, you shouldn’t have anything to worry about, AT THAT TIME.

Great!! Thanks to all.