You're starting water is 625? I'd say you need to use RO and calmag and leave that hard water in the ground.

And when your using r/o water ( dirt 100% right )+ add a uv bulb for 99.9% germ killing prevention. water in growing is key!

Mantinian said:

Hello . First time grower . My ppm is 625 do I need to use Calmag?

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If your water, before you add nutes, is 625, you probably won't need a drop of calmag. This mostly depends on what's already in your water.
If you can find out at least a general idea of what's already in your water, it will make mixing nutrients a lot easier.

I grew with 650ppm well water for YEARS with absolutely no problems. Until I got a specific strain that just didn't agree with it, then I finally broke down and bought an RO system for 60 bucks off Amazon. Dont waste money on anything more than 3 stage RO system for growing, anything more is overkill.

You can usually find out what's in your water if you search around on Google enough. If you know what aquifers are in your area they will have reports on minerals found in their water, this is usually pretty close to what you are going to get out of your well. Assuming you have well water. At 625ppm I sure hope it's well water

625 starting ppm? Woof. That's hard.

I would find a hard water formula from General Hydroponics, Veg+Bloom or Jack's tap. They typically use nitric acid to help keep the pH lower with that many minerals in the water.