Before any hobbyist goes and uses straight dolomite, I will reiterate on of my key points about farms/shops not being the same as a hobbyist tank. While vendors move out a lot of water when they sell frags (as well as massive water changes), the high levels of magnesium probably do not have a chance to accumulate like they would in a hobbyist tank.
I took a trip down the man-made reactor media highway (AquaMedic) which was pure calcium carbonate. It had no strontium or magnesium (or other traces), so I had to use some Dolomite in with it. If I used too much Dolomite, the magnesium level would slowly rise in the tank and could have gotten dangerous.
In short, if you are not moving out water or watching your tanks as much as WWC, then don't try to be too much like them - study and learn, but understand that a hobbyist is not a retail shop.