Tds meter & how to use it

I have a tds meter, but honestly not sure what im testing & what sort of numbers im looking for? I hear about people checking runoff from their catch trays, but no idea what to do with the info from testing it?

It’s simple.

You are measuring the amount of dissolved solids in your water. Think of the water you are using on your plants as a large apartment building unit and the tenants are your nutrients.

You want the right amount of “good tenants” in your building, not too many or too few.

And it will vary depending on the medium you are using. Hydroponic is for me a love hate relationship but is very rewarding you literally get to micromanage every tenant in your building.

Your tenants will be micro and macro nutrients, and your TDS meter let’s you know how many tenants live in your building.

I hope I didn’t complicated things.


@mikes As Gabo stated you are measuring what is in your water. For Hydroponics first understand what your base water PPM measurement is. DI water will be 0PPM and tap water will be around 300ppm. Now when you add your nutrients you can measure again to see where your nutrients brought the PPM level to. Depending on growth stage you will need different levels of nutrients and the TDS meter helps you to know you have these levels in your water solution. Each grower will have different numbers they look for based on their system. Remember it measures anything in the water so keep this in mind as well to help with advanced issues. In your most aggressive nutrient solution I think most would agree to not exceed 1000PPM of nutrients and for your least aggressive, seedlings, not more than 200ppm. I do not think measuring a dirt runoff PPM would help much under normal conditions. Make sure to keep your TDS meter probe moist and not let the tip dry out or else it may need calibration. Keep the cap on but a little moisture in there is recommended.


ok, thank you for the info, im growing in soil but now i have a better idea what to look for as far as numbers…now if i can only figure out how to post pics again…??

yeah, that worked one time, then tried the same thing with more pics from my laptop then i would get a pop up saying file is too large, try sending it to a cloud service then upload from there?

1 Like

Hmm I can’t say I had that issue :thinking:. Lest see if the forum eagle God’s can help us.

i did send a msg to Gareth, see if i get a response? not sure who that is, but its a cool name! :sunglasses:

1 Like

I’m back… so when we look at ppm/tds I get the range. I’m assuming adding the nutes is what increases the base number, right?

@GrnyGrows yes, sounds like you get it

1 Like

So, do you think I’m ready to pull the dang plug :crazy_face: ? The room build will be complete tomorrow. Will test temp/RH and light settings. Haven’t been able to do them all at once yet. I’m nervous but stoked.

1 Like

lets do the damn thing! :cowboy_hat_face:

1 Like

Yee haw. Thanks for everything. I appreciate you.

1 Like

just remember not to react to every little non conformity in your plants. Sometimes a non conforming leaf is nothing more than a leaf the plant doesn’t want…one bad leaf does not make for a problem plant…

1 Like

You’re getting to know me. Yes, I’m a worrier. KISS and don’t panic… My new motto.

1 Like