SPS corals, 15 honest profiles.

SPS means small-polyp stony: dense skeletons covered in polyps a millimetre or two across, growing into branches, plates, encrusting sheets and mounds. They pull calcium and carbonate out of the water fast, so a colony of any size needs alkalinity held in a narrow band day after day - dosing or a calcium reactor, plus strong light and turbulent flow. They suit a reefer who already tests regularly and whose tank has been boring for months. The trade-off is bluntly stated: SPS punish swings that softies shrug off, and a single alkalinity crash can strip the tissue overnight. Not all are equal, though - pavona, cyphastrea and leptastrea are far steadier than acropora, and make a fairer first attempt. Porites, despite its solid look, is not among them - colonies often decline slowly even in good tanks.