Porites cylindrica

Porites cylindrica is a stony coral made of thick, cylindrical finger branches that builds wide clumps as it grows. Its polyps are very small and stay open during the day too, so the surface looks soft and fuzzy. Its bright yellow form is the best known in the hobby; green and bluish forms also exist. When newly arrived it can take time to adjust to the light and its spot, but once settled it is hardy and resistant to disease. Trade in stony corals is subject to CITES Appendix II; choose an aquacultured frag.

• Light: Moderate to high light; roughly 150–250 PAR. If light is insufficient, the yellow color turns mustard or golden brown.
• Flow: Strong, random flow that reaches the branches. If flow is weak, the surface becomes coated with detritus, the polyps do not open and the tissue slowly dies.
• Placement: An open ledge in the upper half of the rockwork.
• Water parameters: Salinity 1.025–1.026, KH 7–9 dKH, calcium 400–450 mg/L, magnesium 1250–1400 mg/L, nitrate 2–10 mg/L, phosphate 0.02–0.08 mg/L.

It is photosynthetic; it gets most of its energy from zooxanthellae algae. Phytoplankton or very fine powdered food given while the polyps are open can speed up growth; this is not essential.

It is a peaceful coral, but it is easily stung by other corals; leave at least 5–8 cm of space. Dwarf angelfish and butterflyfish may pick at the polyps. Small, yellowish-white Porites-eating nudibranchs (Phestilla lugubris) are dangerous; inspect new pieces carefully and put them through a coral dip. The Montipora nudibranch has also been observed attacking this species.