Hmmm, have it grow in a form that traps rainwater and attracts insects and the energy problem is solved, leaving "only" the skeleton problem.
Reuse the kitin from the insects perhaps?
Would be very slow growing, but that's not a problem for coral.

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‘To those who regard “crime fiction” as some sacred icon which must follow a rigid formula, I will always be the man who writes 18-syllable haiku.’Trying to make sense of computers, The Error Log.