> But even if they could it is not a long term solution, as ocean acidification means that reefs are become gradually non viable everywhere.

More metabolic stress and lower calcification rates but to my knowledge there isn't research to support projected ocean pH making reefs nonviable globally. The photic zone in which reefs grow will still be a good ways off from the CaCO3 saturation depth, although some deepwater mesophotic reefs and regions, less so. Heatwaves will remain the dominant threat for a while yet.