SPS (Small Polyp Stony) corals

Hard corals with small polyps. They are the builders of coral reefs and represent the greatest challenge in marine aquariums.

Detailed explanation

SPS are madreporous corals with a dense calcareous skeleton and very small polyps. The best known genera are Acropora, Montipora, Pocillopora, Stylophora and Seriatopora.

They require perfect conditions: intense lighting (300-500 PAR), strong and turbulent flow, very stable water parameters. Any swing in KH, calcium or temperature stresses them. They are the first to react when something is wrong in the aquarium.

The growth of SPS depends on the consumption of calcium and KH. An aquarium full of Acropora can consume 2-3 dKH per day. The balling method or a calcium reactor become indispensable.

The colouration of SPS depends on the interaction between zooxanthellae (symbiotic algae) and protective coral pigments. Too much light fades colours. Little light makes them brown. Finding the right spot requires patience and observation.

Nutrients play an important role. Contrary to popular belief, SPSs do not want sterile water. Some nitrates (2-5 ppm) and phosphates (0.02-0.05 ppm) are needed by zooxanthellae for photosynthesis. Too clean aquariums produce pale and fragile corals.

Acclimatization of a new SPS must be gradual. We start from the lower area of ​​the aquarium with moderate light and gradually move up over a period of weeks.

The most common diseases are STN (Slow Tissue Necrosis) and RTN (Rapid Tissue Necrosis). The RTN can destroy an entire colony in a few hours. It is often caused by changes in parameters or transport stress.

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