Ah! More great advice! Thanks, y'all!
So I started the water change I had already planned due to last week's Nitrate/Nitrite spike. One snip (no razor blades in this beard-o's apt.) with no pause, and 5 fresh gallons of water later, the small colony & frag colony are separated.
The large colony is now in the 75g, opening up less than ˝ hour after the surgery. The operation was a success...both patients are happy!
No other corals are/were within 8" of the "wound" site.
You guys & gals are awesome!
[Edit: Been using carbon since Day 1]