Advice needed on calmag and other required nutes

Hi guys I live in Scotland where we have very soft water 20ppm do you guys recommending a lot of cal mag when feeding even when topping up with plain water no nutes il growing in dwc thanks for any help as it makes my ppm readings sky high constantly


I’ve never once added it and I’ve been at it since the late 90’s. Use a good hydroponic nutrient like GH 3 part and it has enough. Soil ferts may lack cal mag because the soil already has it.The only reason to add it would be if your fertilizer doesn’t contain it. If your using a complete hydroponic fertilizer and are really concerned about it add a bit of epsom salt to make calcium more available. When you add plain water take a ppm measurement to get back in the ball park or mark your level and fill it to that when replenishing.I don’t know who started the calmag thing but it sure took off. Best of luck.


I’ve also been going for years and never need calmag, my water doesn’t trigger my truncheon it’s very similiar to your water.
As pointed out by @Buzz I’m using nutrient with them added so it’s not needed (canna a+b and coco)

You can buy a kg of calcium chloride and a kg of magnesium sulphate for around £12
If you ever do need either you can treat calcium issues with calcium and magnesium with magnesium instead of lumping the two together.


I would never add anything extra unless I was troubleshooting a visible issue with the plants growth, basically believing that if its not broken… don’t try to fix it. I live in San Francisco and have very low ppm’s from my tap too. If you are starting with a complete, well-balanced, fertilizer, Cal-mag shouldn’t be needed: A complete fertilizer will provide everything your plants need.
Most multi-part fertilizers have a single component which provides the calcium, and which can be adjusted if you so desire; for example – with a 3-part nutrient like General Hydroponics Flora series, you could temporarily increase the proportions of the micro component to increase your Calcium levels. With a fertilizer like Jacks 321, you would be able to increase the Calcium Nitrate levels to increase your total dissolved calcium.

But, ultimately, you should not need to add more calcium to a well-balanced fertilizer


Very generally speaking, plants grown under LED lighting often need additional magnesium. IMO this is the biggest reason you seem to see more & more calmag talk as time goes by.


I used to grow in soil and used epsom salts and biobizz products keeping it all organic 12/12 from seed many moons ago however since switching to rdwc then to dwc ive always had calcium deficiencies and switched from 600 watt hps in cooltube then to spiderfarmer se3000 now back to 600watt hps without cooltube as I always thought I had lighting issues but since starting the calmag they’ve all been fine???