Before you start adding products to increase minerals, you need to know what will be living in the tank. Some of the products mentioned are fine for increasing hardness for plants, but not fish (not enough). There are products for fish out there. And there is a less expensive way than using these, and that is a calcareous substance like dolomite or aragonite in the filter or as a substrate. Not all of what I've mentioned suits every situation, so first can you tell us exactly what fish, invertebrates and plants are intended. If the photo posted earlier in this thread is the tank, fine, all we need to know is what fish and/or invertebrates are intended.
I have near-zero GH and KH out of the tap. The two are usually close (in terms of being high or low), but as Quantum mentioned not always. And by the way, to sort out the terminology, GH refers to general hardness which to aquarists is the calcium and magnesium (primarily) mineral salts in the water, and this is what your test kits measure. TDS (total dissolved solids) is also a part of GH but not something tested by these kits, but i needn't get into that here. The KH is the carbonate or bicarbonate hardness, often called Alkalinity, which is what acts as a buffer to maintain a steady pH, and the higher the KH the stronger the buffer capacity. Attempts to adjust pH down will be futile unless the KH is first reduced. You can read more about how all this works together here: http://www.tropicalfishkeeping.com/f...quarium-73276/
You did mention shrimp initially, and these need calcium for their exoskeletons, so using magnesium will not suffice. But as I said, when we know what fish and invertebrates are intended, we can discuss specifics.