TDS meter

First I'd like to say that this is by far the best educational site for finding all the answers for my first time grow. Thank you
I'll brief you on my system. Using an ebb flow 6 site, 5 gal res. 400w mh, 4' x 2' x 5' grow room, some pots all hydroton some hydroton & rockwool, ro drinking water (ppm 0-7), GH flora series nutrients, and superthrive add.
My question. Used GH recommended amount of nutrients in 5 gal. res. my TDS reading is around 230 I'v seen where the recomindations for ppm is from 400 - 1000. My water (RO) has a ppm of 0-7. Now this solution mix is aggressive grow according to GH website. Is this ok?
#2 Do you reccomend using hydroton or rockwool, or both for this system. It seems I was over watering rockwool at 15min every 2 hr.
Ebb flow users any input or recomindations for this new grower would be appreciated.

I'd use both, the cube in the rocks.

PPM for Hanna Chart PPM


Seedlings, Early Sprouts 100 to 250

Early Vegging 300 to 400

Full Vegetation 450 to 700

Early Blooming 750 to 950

Full Mature Blooms 1000 to 1600

Note: EC Calculations are different, here's a conversion chart :
heres a great chart that shows how different PPM can be from meter to meter... EC is the only real universal language...

Roseman said:

I'd use both, the cube in the rocks.

PPM for Hanna Chart PPM


Seedlings, Early Sprouts 100 to 250

Early Vegging 300 to 400

Full Vegetation 450 to 700

Early Blooming 750 to 950

Full Mature Blooms 1000 to 1600

Note: EC Calculations are different, here's a conversion chart :
heres a great chart that shows how different PPM can be from meter to meter... EC is the only real universal language...

Click to expand...

My meter is a HM digital meter that has been factory calibrated to 342 ppm. Does your water ppm effect your solution ppm?

Could I use a voltmeter (for like.. batteries and shit) as a TDS meter? A voltmeter should still be able to read the EC of the water, no?

Morning Dew said:

My meter is a HM digital meter that has been factory calibrated to 342 ppm. Does your water ppm effect your solution ppm?

Click to expand...

If you have very hard water, you will have a ppm for the water of 150 to 300. I think most growers with a ppm meter subtract that water ppm from the desired nutrient ppm.

SenorSanteria said:

Could I use a voltmeter (for like.. batteries and shit) as a TDS meter? A voltmeter should still be able to read the EC of the water, no?

Click to expand...

Great question, but I don't know the answer.

Roseman said:

Great question, but I don't know the answer.

Click to expand...

Im not very good with stuff like this...

I did some searching, and cant tell is this contains my answer. I'm going to mess around with the voltmeter and some water, and see what I can get to happen. If a voltmeter will work as an EC meter, it would be a pretty cost effective way of checking your nute solution. I got my voltmeter at walmart for like 12 bucks.

Found this: http://blea.ch/wiki/index.php/PPM_Meter#Measuring_PPM.2FEC.2FTDS

Looks like its not as simple as I was hoping it to be. I took a cup of water and stuck the two probes in it 1cm apart, and the only setting that registered anything was called "X1K." After adding 2 gallons worth of nutrient solution to an 8 oz glass of water, I re-checked using the X1K setting. There seems to be a difference, but its rather inconsistent. At first it looked like the nutrient solution raised the EC, but about 10sec after putting the probes in, the conductivity started to fall, and it can be manipulated by moving the probes around in the water. I dont think this is an effective way of measuring PPM, unfortunately. I do think this has the potential to work, but I dont think its simple enough to warrant buying a voltmeter instead of an EC meter.

SenorSanteria said:

Found this: http://blea.ch/wiki/index.php/PPM_Meter#Measuring_PPM.2FEC.2FTDS

Looks like its not as simple as I was hoping it to be. I took a cup of water and stuck the two probes in it 1cm apart, and the only setting that registered anything was called "X1K." After adding 2 gallons worth of nutrient solution to an 8 oz glass of water, I re-checked using the X1K setting. There seems to be a difference, but its rather inconsistent. At first it looked like the nutrient solution raised the EC, but about 10sec after putting the probes in, the conductivity started to fall, and it can be manipulated by moving the probes around in the water. I dont think this is an effective way of measuring PPM, unfortunately. I do think this has the potential to work, but I dont think its simple enough to warrant buying a voltmeter instead of an EC meter.

Click to expand...

I gave ya PLUS REP for trying.

Hah, thanks- i gotcha back.

This would have been awesome if it worked. Wouldnt have had to buy an EC meter... ah well...

Although if i gotta buy more shit, I might go for a UVB bulb first... I am a dirt grower after all.