I've never fragged anything after lights out, never had a problem.
You don't want to do it in the tank though. Use a bowl of tank water to cut them in and have another bowl of tank water handy to drop the cuttings in. I also use Kent Tech D to dip both the parent colonies and the frags in before they go back in the tank. It helps prevent infections.
Also, after fragging any softies, I'd highly recommend running some GAC
. And, if you are fragging any types of polyps, was your hands *well* and consider wearing some sort of eye protection while fragging. The *palytoxin* these contain is extremely dangerous. No kids or pets near the fragging, dispose of the "frag
water" carefully. Use gloves, wash hands, etc. well.
Don't do what I did and off-handedly rub the side of your mouth with your hand before washing. I walked around with a novocaine-numb mouth for a couple days, and the symptoms/results can be much
more serious than that.