Reef Crystal IO salt

[Coleus]

Ok

I am about to give up with this reef crystal. I bought another reef crystal IO bucket and mix the salt with RO/DI water and leave it for a day. I also dosed 8 tsp of Seachem Advance Magnesium (which should increase 55 ppm) to the water before adding the salt.

Well. I test the MG with two different test kits and they all come to be around 1200

What am i missing?

If you buy IO salt and bulk Mg from chemmaster, how many tsp do you add to 15 gallon new water?

Thanks.