Birdsnest Coral

Seriatopora hystrix is a thin-branched stony coral known in the hobby by its English name, "birdsnest". The branches taper toward the tip, end in points and fuse where they touch each other, producing a dense bush that looks like a bird's nest. The polyps are arranged in neat rows along the branches; the genus name comes from this arrangement in rows. The most common form is pastel pink; green, cream and blue-tipped forms also exist.

Once acclimated to the aquarium it is a fast-growing, easily propagated species and one of the SPS tried before Acropora. On the other hand, it is sensitive to shipping, sudden changes in light and rising temperature; the first weeks are the riskiest period.

Trade in stony corals is subject to CITES Appendix II. Because the pink birdsnest has long been aquacultured, it is easy to find as a frag; choose one instead of a wild-collected colony.

• Pink birdsnest: The most common form in the hobby; pastel pink branches.
• Green and cream forms: Seen less often; some of those sold as green birdsnest are actually the thick-branched S. caliendrum.
• Blue-tipped forms: Colonies with bluish tips, sold under the name "Ponape".

It lives on reef slopes and in lagoons from the Red Sea to the Central Pacific. The thickness and density of the branches vary with the environment: in strong flow the branches are short, stubby and dense; in calm, shaded places they are long, thin and sparse. In the wild, guard crabs (Trapezia) may live between the branches.

• Light: Moderate to high light; roughly 150–300 PAR. The color of the pink form becomes pronounced at around 200 PAR and may fade under very strong light. A new frag should be kept at around 150 PAR for about a week and then moved to its spot.
• Flow: Moderate to strong, indirect and random flow. Harsh flow hitting it directly breaks the thin branches and strips the tissue; in very weak flow detritus builds up between the branches.
• Placement: The upper half of the rockwork, on a solid base with 10 cm of space around it.
• Water parameters: Salinity 1.025–1.026, temperature 25–26.5°C; above 28°C it bleaches quickly. 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 sensitive to nutrients bottoming out and to sudden changes.

It gets most of its nutrition from the zooxanthellae algae in its tissue. Fine powdered food, rotifers or amino acid supplements spread through the water by the flow once or twice a week can support growth. Extra feeding is not required; overfeeding brings algae and browning.

It is not an aggressive species; its dense branches only shade the surfaces they touch and grow over them. It is itself an easy target for long-tentacled LPS and soft corals; leave 10 cm of space.

Dwarf angelfish and butterflyfish may pick at the polyps. Small guard crabs (Trapezia) may arrive with wild colonies; they do not harm the coral. Large hermit crabs and sea urchins can break the thin branches.

It is one of the easiest stony corals to propagate in the aquarium. A 3–4 cm branch tip is snapped off by hand or with coral cutters and attached to a frag plug with gel glue; the cut tip heals within a few days. The species can also reproduce by releasing larvae (planulae); new small colonies may appear on their own in the aquarium.

• Branches whitening from the base: Tissue usually recedes upward from the base (STN). Sudden KH or temperature changes and depleted nutrients are the main causes. Cut off the healthy tips and save them as separate frags.
• Rapid tissue loss and bleaching: Temperature exceeding 28°C or shipping stress can kill the colony within a few days. Check the heater and fan settings; under severe stress the polyps may abandon the skeleton.
• Browning: Light is too low or nitrate and phosphate are high.