Goniopora tenuidens

Goniopora tenuidens is a flowerpot coral with a better record in captivity than its genus usually manages. A settled colony forms a solid hemispherical or irregular mound, and from each small, rounded corallite rises a polyp of regular length topped with a uniform bundle of tentacles — 24 to a polyp, the count that separates Goniopora from Alveopora and its 12. The AIMS coral fact sheet description, carried in the species' reference summaries, notes bluish, green, or brown colouring in the wild with tentacles that may be tipped with white. The colonies the aquarium trade imports lean purple and blue, from a faint wash to a saturated violet, with pink and bubblegum forms turning up regularly in aquaculture.

The species was described by Quelch in 1886, originally placed in Rhodaraea, and sits in the family Poritidae in the World Register of Marine Species. Its range covers much of the tropical Indo-Pacific: from Madagascar, the Red Sea, and the Gulf of Aden across the Indian Ocean to Southeast Asia, Indonesia, Japan, the South China Sea, northern and eastern Australia, and the island groups of the western Pacific. It lives subtidally in varied reef habitats and lagoons down to about 30 metres. The IUCN lists it as Least Concern — a common species with a wide range, noted as more resistant to bleaching and disease than many corals — and like all Goniopora it moves in the aquarium trade under CITES Appendix II.

Aquaculturist Justin Credabel, who has established dozens of Goniopora strains at a Los Angeles facility and counts this species among his favourites, describes two forms in the trade. One comes from lagoon-type environments; the other is collected from reefs. Most imports wear some shade of purple or blue. Reef-collected colonies can carry several rings of colour, the yellow-centred "eyes" that recur across Goniopora colour patterns, and bright purple acrospheres — the small ball tips at the ends of the tentacles. That range is worth knowing at purchase time: two colonies sold under this one name can look quite different, and both can be correctly labelled.

The genus earned its difficult reputation honestly, and the history belongs in this entry because this species is one of the exceptions that revised it. Wild flowerpots of the early hobby — mostly Goniopora stokesi — would arrive glorious, hold for three to six months, then refuse to open and die back to a white skeleton, a delayed decline Tidal Gardens describes as deceptive enough to lull the keeper into a sense of accomplishment first. Top Shelf Aquatics puts early wild-collected success below 20 percent and properly kept aquacultured specimens at roughly 80 percent survival through the first year. Goniopora tenuidens is one of the species that turned those numbers around: it is farmed widely, it usually arrives already adapted to captive conditions, and care sources that rate the genus species by species place it at the forgiving end, beside G. lobata and well ahead of G. stokesi.

Light and flow follow the genus pattern at moderate settings. Tidal Gardens recommends 75–125 PAR for Goniopora and has grown the genus from about 40–50 PAR up to more than 200 PAR, favouring the lower end when in doubt because excess light bleaches and there is little advantage in pushing intensity. Start a new colony low, raise light gradually over weeks, and read the polyps: full, even extension through the day is the sign the level suits it. Flow should be low to moderate, indirect, and preferably random — enough to keep the tentacles swaying gently and to carry food and waste past the colony. A powerhead aimed straight at the colony from close range can kill tissue at the contact point and start a chain reaction through the rest of the colony; tentacles thrashing violently are the signal to move it somewhere calmer.

Feeding is the centre of this coral's care. Goniopora are photosynthetic, and light alone kept colonies alive just long enough to starve slowly in the early hobby; the modern turn in flowerpot survival tracks the rise of regular feeding. The working routine across the sources read is fine-particle food two to three times a week — powdered plankton blends made for Goniopora, rotifers, phytoplankton as system food, and liquid amino acids — with the pumps paused for fifteen to twenty minutes while a gentle cloud of food settles over the colony. The feeding response is easy to miss if you expect a show: Tidal Gardens describes an irregular, jerky bobbing, one tentacle at a time, quite different from the fast full-colony retraction of a stress response. Feed consistently and watch extension and growth over weeks rather than days, and ease off if nitrate and phosphate climb — overfeeding a small system undoes the water quality the coral also depends on.

Reef To Go's standard reef parameters suit it: 77–79°F, salinity near 35 ppt (about 1.024–1.026), alkalinity 8–10 dKH, calcium 400–450 ppm. Layered over that base, Goniopora ask for two things some reefs deny them. Alkalinity stability matters more than any single value — Top Shelf Aquatics calls it the most critical parameter for long-term success in the genus, with swings triggering tissue recession even in settled colonies. And the water must carry some food value: detectable nitrate and phosphate. The working consensus in the Tidal Gardens guide is phosphate around 0.05 ppm and nitrate in the 10–20 ppm band, and ultra-clean systems with nutrients at zero are a documented failure mode for the genus — tissue thins and recedes on a coral that is being starved from both directions.

Give the colony room. Fully open, a Goniopora presents far larger than its skeleton, and soft tissue that rubs rock, glass, or a neighbour's skeleton irritates and retracts. This species tolerates colonies of its own kind and will grow right up against them, but it is chemically defended against everything else: Credabel records it producing many allelopathic compounds that inhibit other Goniopora species and other corals, and winning its fights against Goniopora planulata. Keep it clear of other flowerpot species and of LPS with long sweepers, and let its own patch of sand bed or low rockwork belong to it.

Choosing a specimen decides most of the outcome before the coral reaches your tank. Prefer an aquacultured colony — for this species, farmed stock is common, and it is the single largest survival difference the sources describe. Look for full polyp extension in the shop, tight tissue over the whole skeleton with no pale, receding margin at the base, and colour held evenly across the colony. Handle a new colony by its skeleton or base only; the expanded polyps tear easily, and tissue damage is the opening most flowerpot declines walk through.

Field notes — what keepers report

- Manganese is the most debated supplement in the Goniopora threads, and both camps have results to point at. In a long Reef2Reef discussion of long-term Goniopora keeping, several keepers credit manganese dosing — often with iron — for turning colonies around: one reports gonis that always faded away thriving once manganese was dosed every other day, with no special target feeding; another pairs manganese with getting nitrate and phosphate off zero and feeding heavily. Tidal Gardens gives the idea a mechanism from a study it cites — manganese appears to help corals resist stress and bleaching, acting as an antioxidant — while noting that its own systems usually rely on water changes to replenish trace elements. The counterweight in the same thread is blunt: a long-time keeper argues there is no secret sauce at all, that the early gonis were wild Goniopora stokesi that starved, and that certified aquacultured stock today grows for years on normal reef parameters with no special dosing. This entry records the dosing reports as keeper experience, not as a requirement.

- Feeding itself splits keepers into two working camps, and the disagreement is about mechanism as much as practice. Tidal Gardens is convinced Goniopora must be fed, and fed a lot, and traces its own failures to neglect; the TSA and Manta guides both build two-to-three-times-weekly feeding into standard care. Against that, keepers in the same Reef2Reef thread thrive without any target feeding at all, relying on broadcast phytoplankton and amino-acid supplements, and one experienced keeper argues Gonis take in very little particulate food in a tank — that what looks like feeding is largely uptake of dissolved organics and amino acids from the water, a view Tidal Gardens itself raises when it notes some believe the coral takes in nutrients through its skin more than through its mouths. The practical middle every camp shares: colonies in fed systems do better than colonies in sterile ones, whether the food arrives as particles or dissolved.

- Light tolerance is wider in keeper tanks than the care guides suggest. Published guidance clusters at moderate levels — Tidal Gardens recommends 75–125 PAR, one experienced thread contributor puts most gonis at 50–150 PAR. Yet the same discussion includes colonies thriving at 200–300 PAR after a gradual weekly ramp, including one moved to the top of the tank for space and doing well there; the cautionary detail from that keeper is that the corals lost during the ramp were already in poor condition beforehand, while healthy colonies adapted. Acclimation speed and the colony's condition on arrival read as the real variables behind the conflicting numbers.

- Nutrients and magnesium come up together in keeper reports. One keeper running nitrate 5–10 ppm and phosphate 0.06–0.10 ppm — pausing feeding when phosphate approaches 0.12–0.15 — notices polyp extension dropping when magnesium falls below about 1350 ppm in his system. Tidal Gardens documents the genus thriving at both extremes of tank cleanliness in its own and a colleague's systems, phosphate at 1–2 ppm with nitrate over 50 in one, phosphate undetectable with nitrate at 1 ppm in the other, with amino-acid feeding as the shared practice. Stability, again, is the pattern keepers keep landing on.

- Whether Goniopora colonies can touch is genuinely unsettled, and this species sits on the tolerant side of the record. One thread warning holds that some gonis sting and kill each other at close quarters and that a single stung polyp can close a whole colony and invite infection; the thread's own photos of packed goni gardens drew the opposite observation, with many colonies kept touching without incident. The species-specific record is Credabel's: Goniopora tenuidens tolerates others of its own species and grows against them without fusing, while fighting other species chemically. Same-species grouping reads as low-risk for this entry; mixed-species contact stays a gamble.

- Growth and temperament reports split by source, so the field in this entry says Moderate. Credabel, watching farmed colonies daily, calls the growth slow but steady, showing mostly around the fringes of the colony. Manta's species comparison instead groups tenuidens with G. lobata as the faster-growing, more forgiving species, against slower and more temperamental G. stokesi, and notes wild colonies grow slower than aquacultured ones. Keepers also repeat one handling note in several forms: gonis dislike being moved, sulk for days to weeks after a relocation, and go through still periods before growing again — patience after any move is part of the care.