Coral Types
- SPS — Small Polyp Stony corals
- Stony corals with small polyps and a rigid calcium carbonate skeleton, such as Acropora and Montipora. They usually need strong light, strong flow and very stable alkalinity, calcium and magnesium. Try the dosing calculator.
- LPS — Large Polyp Stony corals
- Stony corals with large, fleshy polyps, such as hammers, torches, frogspawn and acans. Most are more forgiving than SPS, though they still build skeletons and consume alkalinity and calcium. Try the dosing calculator.
- Softies — Soft corals
- Corals without a rigid stony skeleton, such as leathers, Kenya trees and GSP. Mushrooms (corallimorphs) usually get lumped in with softies, though strictly speaking they're a separate group, not true soft corals. Generally the hardiest corals for beginners.
- Acro — Acropora
- The classic high-end SPS genus (plural: Acros). Prized for color and growth forms, and among the most sensitive to swings in parameters.
- Monti — Montipora
- A fast-growing SPS genus with plating, encrusting and branching forms. Often recommended as a first SPS.
- Zoas — Zoanthids (Zoos)
- Colorful colonial button polyps, mostly the genus Zoanthus, sold under hundreds of named color morphs. Some zoanthids can contain palytoxin, so wear gloves and eye protection when handling them.
- Palys — Palythoa
- Zoanthid relatives with larger polyps. Many Palythoa contain palytoxin, a potent toxin. Wear gloves and eye protection, and never boil or pressure-wash rock that has them.
- GSP — Green Star Polyps
- A hardy, fast-spreading soft coral (Briareum / Pachyclavularia) that forms a purple mat with green polyps. Often grown on an isolated rock so it doesn't take over.
- Acan — Acan / Acan Lord
- Micromussa lordhowensis, formerly Acanthastrea lordhowensis. A popular, colorful LPS that feeds readily.
- Blasto — Blastomussa
- An LPS with fleshy, round polyps. Tolerates lower light and flow.
- Lobo — Lobophyllia
- A large-polyp stony coral with fleshy, often brightly colored lobes.
- Digi — Montipora digitata
- A finger-shaped Montipora and a hardy, fast-growing SPS.
- Hammer, Torch, Frogspawn
- Popular LPS with long, flowing tentacles. Older references call them all Euphyllia, though hammers and frogspawn have since been reassigned to Fimbriaphyllia. They have strong sweeper tentacles, so give them room.
- NPS — Non-photosynthetic corals
- Corals without photosynthetic algae (zooxanthellae), such as sun corals and many gorgonians. They rely completely on frequent target feeding rather than light.
Equipment
- ATO — Auto Top-Off
- Automatically replaces evaporated water with fresh RO/DI so salinity stays stable. Top off with fresh water only, never saltwater (unless you're dosing kalkwasser through it).
- RO/DI
- Reverse osmosis plus deionization. Produces pure water for mixing salt and topping off, with a target TDS of 0 ppm.
- Sump
- A secondary tank below or behind the display that holds equipment such as the skimmer, heaters and refugium, and adds water volume.
- Skimmer — Protein Skimmer
- Removes dissolved organics by collecting them in foam. Sometimes abbreviated PS.
- Refugium — Refugium (Fuge)
- A section, often in the sump, for growing macroalgae such as chaeto (Chaetomorpha) to export nutrients and give pods a refuge.
- Powerhead — Powerhead / Wavemaker
- A pump that moves water inside the tank. Controllable wavemakers vary the flow pattern.
- AIO — All-in-One
- An aquarium with built-in filtration chambers, usually at the back, instead of a separate sump.
- HOB — Hang-on-back
- Equipment that hangs on the tank's rim, such as a filter, skimmer or refugium.
- QT — Quarantine tank
- A separate tank for isolating and observing or treating new fish and corals before they go in the display.
- DT — Display tank
- The main aquarium.
- FOWLR — Fish Only With Live Rock
- A saltwater system with fish and live rock but no corals.
- BB — Bare bottom
- A tank with no sand bed. Easier to keep detritus suspended and removed.
- DSB — Deep Sand Bed
- A sand bed roughly 4 inches (10 cm) deep or more, intended to support denitrification in the low-oxygen layers.
- LR — Live rock
- Rock colonized by beneficial bacteria and other life. It's the main biological filter in most reefs.
- LS — Live sand
- Sand colonized by beneficial bacteria and small organisms.
- GFO — Granular Ferric Oxide
- A media that removes phosphate. Run it slowly at first so PO4 doesn't drop too fast.
- GAC — Granular Activated Carbon
- A media that removes organics, odors, color (yellowing) and some toxins.
- ATS — Algae Turf Scrubber
- A device that grows algae under light to export nutrients.
- CUC — Clean-Up Crew
- Snails, hermit crabs and other invertebrates that eat algae and detritus.
Water Chemistry
- Alk — Alkalinity (Alk / dKH)
- A measure of the carbonate buffer that corals use to build skeletons. A common target is 7–9 dKH (many aim for 8–8.5). Raise it by no more than about 1 dKH per day. Try the dosing calculator.
- Ca — Calcium (Ca)
- Typically 400–450 ppm. Raise it by no more than about 50 ppm per day. Try the dosing calculator.
- Mg — Magnesium (Mg)
- Typically 1250–1400 ppm. It helps keep calcium and alkalinity from precipitating. Raise it by no more than about 100 ppm per day. Try the dosing calculator.
- Big-3
- Calcium, alkalinity and magnesium together. Try the dosing calculator.
- SG — Specific Gravity (salinity)
- Most reefs run at an SG of about 1.025–1.026, which is roughly 35 ppt. Use a calibrated refractometer or a conductivity probe to measure it.
- NO3 — Nitrate (NO3)
- The end product of the nitrogen cycle. Most mixed reefs do well around 2–20 ppm. Keep it detectable, not zero.
- PO4 — Phosphate (PO4)
- A nutrient that's useful in small amounts. Many reefs aim for about 0.03–0.1 ppm. Too high fuels algae; bottoming out at zero can starve corals.
- PAR — Photosynthetically Active Radiation
- The intensity of usable light for corals (400–700 nm), measured with a PAR meter.
- TDS — Total Dissolved Solids
- Measured in ppm. Used to check that RO/DI output reads 0 ppm.
- ULNS — Ultra-Low Nutrient System
- A system that runs nitrate and phosphate very low, typically for pastel SPS color. It's less forgiving.
- ICP — ICP testing
- Inductively coupled plasma analysis, sent to a lab, which measures dozens of elements and trace metals.
- Two-Part — 2-part dosing
- A pair of balanced solutions, one supplying calcium (calcium chloride) and one supplying alkalinity (sodium bicarbonate or soda ash), dosed in equal amounts at different times so they replace what corals use without skewing the ion balance. Try the dosing calculator.
- Soda ash — Sodium carbonate
- Sodium bicarbonate that has been baked to drive off CO₂. It raises alkalinity with less product (about 18.9 mg per liter per dKH) and also lifts pH. Use reef or pharmaceutical grade. Try the dosing calculator.
- Bicarb — Sodium bicarbonate
- The pH-neutral alkalinity source (about 30 mg per liter per dKH). Raises alk with only a small pH bump. Use reef or pharmaceutical grade, not kitchen baking soda with additives. Try the dosing calculator.
- CaCl₂ — Calcium chloride dihydrate
- The usual dry calcium supplement and the calcium half of most two-part systems. About 3.67 mg per liter raises calcium 1 ppm. Try the dosing calculator.
- Kalk — Kalkwasser
- Calcium hydroxide dissolved in RO/DI and usually dripped through the top-off. Adds calcium and alkalinity together and raises pH, so dose it slowly. Try the dosing calculator.
- Calcium reactor
- A chamber where CO₂ dissolves calcium carbonate media, returning calcium and alkalinity in natural balance. This is how calcium carbonate is used; it is not dosed directly. Try the dosing calculator.
- meq/L — Milliequivalents per liter
- An alkalinity unit. 1 meq/L equals 2.8 dKH. Try the dosing calculator.
- Dosing pump
- A small programmable pump that adds supplements in many small doses through the day. Try the dosing calculator.
- Trace elements
- Elements such as iodine, strontium, iron and others that corals use in tiny amounts. Usually covered by water changes; dose only based on ICP results. Try the dosing calculator.
- pH
- A measure of acidity. Reefs commonly run about 7.8–8.4. Soda ash and kalkwasser raise it; CO₂ from a calcium reactor lowers it. Try the dosing calculator.
Practices & Slang
- Frag — Frag / Fragging
- Cutting a coral into pieces (frags) to propagate it. Frags are usually glued to frag plugs.
- Acclimation
- Slowly adjusting new livestock to tank water, often by drip acclimation. Many corals instead get a quick temperature match plus a dip.
- Cycling
- Establishing the nitrogen cycle: bacteria convert ammonia to nitrite, then nitrite to nitrate. It usually takes a few weeks.
- WC — Water change
- Replacing part of the tank water with freshly mixed saltwater.
- Dip — Coral dip
- Treating corals in a solution to remove pests before they go in the tank.
- Dosing
- Adding supplements regularly, such as two-part (calcium plus alkalinity), kalkwasser (calcium hydroxide) or magnesium, to replace what corals use. Try the dosing calculator.
- Cooking-rock
- Curing rock in dark tubs of saltwater for weeks, with water changes, so it releases phosphate and decaying organics before use.
- WYSIWYG
- "What you see is what you get." You receive the exact specimen in the photo.
- FTS — Full Tank Shot
- A photo of the whole aquarium.
- LFS — Local Fish Store
- Local Fish Store.
- Reefer
- A reef aquarium hobbyist.
- Mixed-reef
- A tank that keeps SPS, LPS and soft corals together.
- Nano
- A small reef tank, commonly under about 30 gallons (some say 20).
- Hitchhiker
- An unintended organism that arrives on rock or coral. Some are good, some are pests.
- Aussie
- Coral collected from Australian waters, often prized for color.
- PE — Polyp Extension
- How fully a coral's polyps open. It's a common health and comfort indicator.
- Encrusting
- Growing as a thin layer across rock or another surface.
- Browning-out
- A coral losing its bright color and turning brown, often from excess nutrients, too little light, or stress. It's different from bleaching, where the coral turns white.
Problems & Pests
- RTN — RTN / STN
- Rapid and Slow Tissue Necrosis: coral tissue dying off the skeleton, quickly (hours to days) or slowly from the base up. Common in SPS, often linked to parameter swings, especially alkalinity. Try the dosing calculator.
- AEFW — Acropora-Eating Flatworms
- Flatworms that eat Acropora tissue and lay eggs on the skeleton. Dip and inspect every new Acro.
- Cyano
- Cyanobacteria, the "red slime": a photosynthetic bacterium, not true algae.
- Dinos
- Dinoflagellates: algae-like organisms that form stringy or snotty, bubbly films. Often linked to very low nutrients.
- GHA — Green Hair Algae
- A fast-growing filamentous algae, usually fueled by excess nutrients.
- Ich — Marine Ich (Crypto)
- White-spot disease in saltwater fish, caused by the parasite Cryptocaryon irritans. The name is borrowed from freshwater ich, which is a different organism (Ichthyophthirius). Quarantining new fish is the best prevention.
- Aiptasia
- A pest glass anemone that spreads fast and stings corals.
- Red-bugs
- Tiny parasitic copepods (Tegastes acroporanis) that live on Acropora.
- Tank-crash
- A rapid, cascading system failure that kills livestock.
- OTS — Old Tank Syndrome
- A loose term for decline in long-established tanks, often blamed on accumulated detritus or phosphate or on depleted elements. It isn't a precisely defined condition.
Ranges are common hobby targets, not rules. Stability matters more than any single number.