Add one dose, let it cycle for an hour or two for good mixing, and test your magnesium. If it went up by around 50-100, (preferably around 50, in my opinion) then stick with that dose, once daily.
Also dose by "target feeding" the stuff to the bryopsis. Cut off all circulation/return pumps, use a turkey baster to puff it onto the biggest bryopsis patches, and let them stew in it for as long as you feel safe leaving your pumps off (for me, that's about an hour or two). Watch corals carefully and turn on all the pumps if any of them start behaving badly (ie, closing up or wilting).
Obviously you're going to test your magnesium increase on that first dose before you do the above method, just in case your calculation is overkilled. Ie, your first dose just toss it in the sump and leave everything running so you can verify the increase.