It is around 98% pure Magnesium Chloride.
It comes in "Prill" form which is similar to bean bag filling to look at.
Very simple to dose.
1: Take tank reading.
2: If low add specified amount to a jug of Top off water and mix.
3: Chuck in your sump!
Thats it.
I can give you approximate usage per litreage if needed.
The Calcium works exactly the same. No need for Kalk stirrers and all that crap. Just dump straight into the sump.
If no sump, drip feed straight into tank.
My Acros are colourful enough for me and I have been using this system for 4 months odd.
Im not here to make money, just help make reefing easier for everyone!
Craig