Hi Monique,

I have been growing hydroponic vegetables for more than 30 years and I gave conductivity measurements away years ago. There was not much correlation between electrical conductivity and concentration of nutrients.

I adopted a regimen like this:
At the end of each day, fill the nutrient tank with water and adjust the pH to 6.4
On the seventh and fourteenth day, give the nutrient tank one charge of new nutrient solution, top up and adjust the pH tp 6.4
On day 21, dump the nutrient solution and fill up with neat water and pump up to the growing modules and allow to drain ... this is important to flush out un-needed salts.
Then refill with water, add one charge of nutrients, and adjust the pH to 6.4

Using this regimen, I have no need for conductivity measurements. As for the idea of doubling your nutrient solution strength, please read the piece about doing this in the FAQ page on my Australian web site.
Making nutrient solutions too strong can reverse the osmosis process and desiccate the plant instead.

If you still do not understand the process, please feel free to send me an email ... the address is on the web page.

Cheers,
Jimr007
Sunshine Coast
Australia.

Here is a link that might be useful: Simple Sand Hydroponics

monique..Be best if u just add nutes to the reservoir until u reach your goal..Don't know what u are growing but an EC of 4 is pretty high..just do tomatoes and peppers myself.and have bumped them up to 4 but didn't see any real change..unless your are in a GH..I have a micro doser, so bumping up is no problem for me..just set the dial to 4..don't give up on the ec meter..is the easiest to use. Some folks make hydro a real job and it depends on what u really want to do..I just want to have fun and grow good crops..so far so good..
corky

Thanks for both your advice. I've studied Jim's page in detail. I think my confusion is over what plants need how much nutrient solution. I guess I'm sweating the small stuff. *** Within your experience, would there be an issue with planting tomatoes, cukes, peppers, lettuce and beans and feeding them all off of the same nutrient reservior? Thanks for the help!

Hi Monique,

You should have no problem growing all of those vegetables plus Chinese greens all with the one nutrient solution.
Just watch the pH and make certain you use a decent form of Iron. Do not use Ferrous Sulphate as it oxidises too readily in solution and the plant ends up with no Iron.
I see Iron Tartrate used elsewhere on the Internet; this should be OK, but I have never used it.

Cheers,
Jimr007
Australia.

Wow -- that's why my mustard greens are looking chlorotic -- I've been using Ferrous Sulphate. Thank you so much.