Rhipocephalus

Rhipocephalus · also called Pinecone, Pinecone Alga

Rhipocephalus is a heavily calcified green macroalgae that stands upright in sand, with stacked scale-like blades around a stalk giving it a pinecone shape. It deposits calcium carbonate, so it draws down calcium and alkalinity. Few reports describe long-term success, and it can go sexual and die.

Educational only. Some KinStation entries are reviewed by licensed veterinarians, but none can replace an in-person exam. Always consult a licensed veterinarian or board-certified specialist for diagnosis, treatment, or any decision affecting your pet's health.

Quick facts

Category	Marine & Algae
Family	Halimedaceae (older and some recent works use Udoteaceae)
Native origin	Tropical western Atlantic: Caribbean, Bahamas and South Florida
Care difficulty	Advanced
Light	Bright indirect
Pet toxicity	Toxicity unknown

Light

Wants moderate-to-strong reef lighting to support calcification, in line with relatives such as Udotea. It may survive under lower light but grows best with more. Aim for steady, good PAR over the sand bed in a display or refugium, and avoid abrupt changes in intensity.

Water

Standard reef parameters: 23-27 C (74-80 F), salinity ~1.025 SG, pH 8.1-8.4. Because it calcifies heavily, it needs well-maintained calcium (~400-450 ppm), alkalinity (8-11 dKH) and magnesium (~1300 ppm), and it competes with corals for them. Test these often in any tank that holds several calcifying algae.

Soil & potting

Grows from sand, not rock. A mass of rhizoids anchors the stalk, so plant the base into the substrate rather than leaving it loose on top. Wild plants grow in sand and coral rubble among seagrass, so a deep, undisturbed bed is the closest match. Do not tie or glue it to rock.

Environment — humidity, temperature, placement

Native to protected shallows of inner lagoons, seagrass beds and sandy rubble zones in the Caribbean, the Bahamas and South Florida. Give it gentle to moderate flow over an undisturbed sand bed at standard reef temperature, 23-27 C (74-80 F). Works in a lit display or sand-bed refugium.

Propagation

Keepers have little record of trimming or splitting it, so leave plants whole. Like its relatives it can go sexual, turning the thallus into gametes: field work timed this at about 48 hours from first fertility to release, and the dead plant is left behind. Remove it promptly and check water quality.

Toxicity detail

No source covers cats or dogs, so the rating stays unknown. It carries rhipocephalin, a feeding deterrent reported as toxic to fish, on top of its hard skeleton. Most fish and invertebrates avoid eating it. Harm to tank animals from a living plant is not documented, and it is not known to smother corals.

Varieties & cultivars

Natural forms are the wild species; cultivars are selectively-bred colour or variegation forms of the same plant.

Natural forms1

Pinecone

Rhipocephalus phoenix. A heavily calcified green alga that rises out of the sand bed, with stacked scales around a stalk that give it the outline of a pinecone. Most fish and invertebrates avoid eating it.

Set its base in a sand bed. Like its relatives it can go sexual, turning the thallus into gametes and leaving the dead plant behind.