Hello
I picked up cal magic and it says to put 1 teaspoon per gallon but the ppm for that rate are near 500. Should I be doing a lower rate? I’m using reverse osmosis water, so I’m just trying to add some Cal mag back into it. What rate should I be using?
I shoot for 150 ppm cal mag in my nute mix.
Does that reading include your water source? I’ve never seen that amount read 500 PPMs in RO or distilled water 
1 ml of cal magic (Cal mag) added to a gallon of water is only about 40 to 45 ppms. I don’t find it necessary to ever use more than 3 ml per gallon (5 ml max)
Also, you’ll notice that a teaspoon from your kitchen utensil box is different than a teaspoon in true measurements. A true teaspoon is 5 ml
I did a test a while back so i could get a base line of how much all my additives raise EC per gallon. I use cali magic and my blue lab trenchon stick constantly says .2 EC per gal. So basically on the 700 scale thats 140ppm and on 500 scale thats 100ppm. Maybe with a digital readout the ppm might differ slightly but thats what I’ve found. As @OGIncognito added you should see what your ppm of your water is without adding anything first. Hope that helps grow bro
I would verify what scale your tds reader is on. If it’s 700 scale that’s around 360ppm on 500 scale
Ya I’m using RO water. It is my first time using cow magic and when I mix it up, the PMs were coming out to 500. So I wasn’t sure if that was how it’s supposed to be or what’s going on.
I would feed the calmag at 3-5 mills per gallon in the veg stage. Once flowering and you crank the light up start looking to see if there’s any calcium deficiency signs, increase the dose if you see the deficiency. Epsom salts is a great source for magnesium by the way but not needed if you’re using a calmag combo
I use same as @OGIncognito 3 - 5 ml/gal. Calmag eats up a lot of real-estate in EC/ppm total. I’ve found 3ml/gallon using RO water with coco substrate works good for me. But some strains might need a bit more. So i start at 3ml and watch leaves closely for any signs of a deficiency. Gotta catch it quick or you’ll get some leaf destruction for sure.
Good luck grow bro
Switch your meter to EC and see what it reads and let us know. This will tell us what scale your meter is on for ppm
Here are two pics of my tds meter. One is with plain water and the other with 5 ml of calimagic. The calmag puts me at around 450. Using .5 scale
Sounds about right, i find it best to know how much 1ml/gal raises EC/ppm for everything your putting in the water. That way you’ll have a baseline for sanity check.
