Is there any way to farm coral in more temperate waters? Reef fish are very valuable so it could even be commercially viable.
You can't do it in the sea otherwise, because there is not a lot of accurate and still free areas. Coral needs a lot of light. Must be shallow. Pirate and lawful fishing, commercial sea routes, tourism (coral reef attracts big predators like sharks), and a net of vested interests will block it.
And you'll need to wait 3000 years to have a coral reef at '3000 years level', of course. Corals are terribly slow and fight with their neighbors all the time. Such project would be extremely expensive.
Staghorn could make a good skeleton of a reef in, dunno, maybe 50 or 100 years and would attract a wonderful biodiversity if left alone; but is not enough in reef terms. we are talking of the cream of the cream. One of the finest works of this planet. The staghorn ecosystem is just a baby and a lot of species would be sorely missing.