Grow Mediums Calcium confusion

[aristophanes]

I have purchased greenhouse powder feeding short flowering for my upcoming auto grow. This should be fine?

I am doing an led dwc grow in a soft water area. My tap water is 0.09 ec . My local water authority reckons my area has soft water. I am suspicious I'll need calcium supplementation, but I can't use cal mag because my powder feed already supplements iron and magnesium.

Can anybody suggest the cheapest/most efficient way to supplement only calcium in a dwc setup?

Many thanks!

 

[Spanglish]

Could check out the Canna Mono Nutes they do seperate Ca and Mg supplements have used them in the past in soil, but you might want to check up if they are suitable for DWC.

http://www.canna-uk.com/mononutrients