Coral Keeping Glossary

Rapid tissue necrosis, where coral tissue sloughs off within hours to days; mainly in SPS, from combined stressors.

A pest anemone that spreads rapidly in reef tanks and stings corals. Remove early with dips or dedicated methods.

The water's buffering capacity, key to coral skeleton growth; commonly held around 7–11 dKH. Sudden swings can trigger bleaching or RTN.

A cnidarian that hosts clownfish (e.g. carpet, bubble-tip anemones). It can move and sting neighboring corals.

The daily light-on duration; ~8–10 hours is typical for reefs, kept steady by timer with dawn/dusk ramping.

A mushroom-shaped soft coral (Sarcophyton); hardy and beginner-friendly, it periodically sheds a surface film.

Slow tissue necrosis, where coral tissue gradually recedes to expose skeleton; slower than RTN and often stress-driven.

Small-polyp stony corals (e.g. Acropora, Montipora); need strong light, flow, and stable water — advanced level.

Large-polyp stony corals (Euphyllia, Lobophyllia, Goniopora, etc.); many grow well under moderate light.

The large parent colony from which frags are cut; the origin point for tracing a lineage's provenance.

Symbiotic microalgae living in coral tissue; they feed the coral via photosynthesis. Losing them causes bleaching.

The main building block of coral skeleton; commonly kept around 400–450 ppm, balanced with KH and Mg.

Equipment that dissolves media with CO2 to replenish Ca and KH automatically; used in high-demand SPS tanks.

The living tissue connecting polyps across a coral. Its loss, exposing skeleton, signals tissue necrosis (RTN/STN).

A single coral mass of many polyps joined by shared tissue; most reef-building corals grow as colonies.

Observing and treating newly acquired corals in a separate tank before adding them, to prevent pests and disease.

An SPS coral (Montipora) growing in plates or branches; hardier than Acropora and a popular SPS starter.

An auxiliary tank (often below the display) housing the skimmer and heater; adds volume and stabilizes water quality.

A bivalve (Tridacna) with a colorful mantle; hosts zooxanthellae and grows under light. Listed on CITES Appendix II.

Loss of zooxanthellae from stress, turning corals white; caused by heat, light shifts, or poor water. Can be fatal if prolonged.

Flow that delivers oxygen and food to corals and clears waste; SPS prefer strong flow, soft/LPS gentler.

A mat-forming soft coral (Clavularia/Pachyclavularia); hardy and good for covering the base rock.

Corals without a hard skeleton (leathers, Xenia, etc.); many are hardy and beginner-friendly.

Establishing filter bacteria in a new tank so ammonia→nitrite→nitrate breaks down; essential before adding corals.

Disc-shaped corallimorphs (Discosoma/Ricordea); hardy in low light, no skeleton, and not CITES-listed.

Soaking corals in a treatment solution before adding them to remove flatworms and pests; pairs well with quarantine.

Supplements replacing consumed Ca, KH, Mg, and trace elements; planned dosing is vital in SPS-heavy tanks.

A small reef tank (roughly under 40 L); water parameters shift easily, so frequent care is needed.

An LPS (Euphyllia) with flowing tentacles — hammer, torch, frogspawn types; a popular entry-to-mid coral.

A measure of photosynthetically active light reaching corals; targets vary (low for soft, high for SPS), best checked with a PAR meter.

Saltwater salinity, typically held at SG 1.024–1.026 (~34–35 ppt); it rises with evaporation, corrected by top-off.

A small piece cut from a colony, mounted on a plug; frags carry a lineage forward as they're shared.

A core marine filtration device that removes organics via fine bubbles, curbing nutrient buildup.

An element that stabilizes Ca and KH, kept around 1250–1400 ppm; low Mg makes Ca/KH hard to hold.

Hardy colonial polyps (Zoanthus/Palythoa) in many colors, popular as frags; handle Palythoa with care (toxin).

The iconic branching SPS (Acropora); prized for growth and color but demands strong light, flow, and very stable water.

Oxygen dissolved in water, needed for corals and livestock to respire; maintained by good flow and gas exchange.

Aragonite sand seeded with beneficial bacteria for marine tanks; provides biological filtration on the bottom.

Porous rock colonized by bacteria and microfauna; the biological and aesthetic backbone of a marine tank.