Acropora is the most species-rich coral genus on Earth, with 150+ recognized species spanning the Indo-Pacific. The hobby has carved out about 50-60 species and dozens of named cultivar lineages from Acropora millepora, A. tenuis, A. tortuosa, A. echinata, A. hyacinthus, A. valida, and others. Acropora is the centerpiece genus for SPS reef-keepers and the genus that distinguishes a "mixed reef" from an "SPS-dominant reef."
Acropora demands stable parameters above all else. Alkalinity swings of more than 0.3 dKH in 24 hours trigger STN (slow tissue necrosis); swings of 1+ dKH trigger RTN (rapid tissue necrosis) that can kill a colony in 48 hours. Beyond chemistry, Acropora needs intense light (200-450 PAR depending on species) and turbulent flow (30-60x turnover for demanding species).