I don't know if you have done this yet but I was just talking to a fellow reefer about it and here's what he said:
Oh hey Sherri,
I've been doing some research for my presentation, and might have a way to frag your wall hammer. Though to me this is pretty extreme.
Question though... is the Wall Hammer kind of like a Bubble Coral where there's a central skeleton and then the larger fleshy part?
If so... there's a technique (I may mention in the presentation - though I don't think I'd actually ever try it),
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With bubble corals basically you can do this:
Dremel Tool the skeletal base to make a "fissure" of sorts vertically. Almost like slicing the skeleton in half but you stop just short of the fleshy part.
Then off-set the cut vertically, but only a very little. You do NOT want to damage the fleshy part at all.
Then insert plastic wedges to the crack and VERY slowly (over the course of 2-3 weeks) widen the split.
This causes the fleshy part to stretch and eventually (slowly) split on it's own into two halves, each on it's own skeleton.
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To me this is really extreme, but a method where I thought there actually was none.