Reef hobby glossary
The reef-tank vocabulary, alphabetized. 52 terms, each with a short definition and a link to a deeper reference.
A
- AEFWAcropora-Eating Flatworm. Pest specific to Acropora corals.
- AI Prime / HydraAqua Illumination LED reef lights. Hydra 32/64 HD are the popular SPS-grade fixtures.
- AIOAll-In-One — a tank with built-in rear filtration chamber instead of an external sump.
- AlkalinityWater's capacity to neutralize acid. Reported as dKH, meq/L, or ppm CaCO₃.
- Apex (Neptune)Apex controller from Neptune Systems. Industry-standard reef automation.
- ATOAuto Top-Off. Adds RODI water to replace evaporation.
B
C
- CalciumCa²⁺. Reef target: 380–450 ppm (most stable reefs sit at 420–440).
- Calcium reactorAragonite media chamber that dissolves under CO₂-driven pH 6.5 effluent.
- Carbon dosingAdding vodka, vinegar, or biopellets to drive bacterial nitrate consumption.
- Cleanup crew (CUC)Snails, crabs, urchins, and shrimp added to graze algae and detritus.
- Cyanobacteria (cyano)Bacterial red / black slime that sheets across surfaces.
- CyclingThe 4–6 week process of establishing nitrifying bacteria in a new tank.
D
- Dinoflagellates (dinos)Single-celled algae that thrive in low-nutrient reef tanks.
- dKHDegrees of carbonate hardness — a German alkalinity scale. 1 dKH = 17.86 mg/L CaCO₃ = 0.3566 meq/L.
- DLIDaily Light Integral. Photons delivered to the substrate per square meter per day.
- DSBDeep Sand Bed. 4+ inches of fine aragonite for anaerobic denitrification.
F
G
I
K
L
M
N
P
- PARPhotosynthetically Active Radiation. 400–700 nm. Measured in µmol photons/m²/s.
- pHAcidity / alkalinity scale. Reef target: 8.1–8.4.
- Phosphate (PO₄³⁻)Reef target: 0.03–0.08 ppm.
- Protein skimmerFoam-based mechanical filter that removes organic compounds before they break down.
- PURPhotosynthetically Usable Radiation. The PAR subset that zooxanthellae pigments actually absorb.
Q
R
S
- SalinityTotal dissolved salt content. Reef target: 35 ppt (SG 1.0264 @ 25 °C).
- Soft coralsNon-stony corals. Mushrooms, zoanthids, leathers, xenia, gorgonians.
- Specific gravity (SG)Density of saltwater relative to fresh. NSW at 35 ppt = SG 1.0264 @ 25 °C.
- SPSSmall Polyp Stony coral. Acropora, Montipora, Pocillopora, Stylophora.
- StockingThe fish and inverts inhabiting a tank.
- SumpAuxiliary tank plumbed below the display for filtration equipment.
T
- Tang policeHobbyist consensus on minimum tank sizes for tang fish.
- Trident (Neptune)Automated alkalinity / calcium / magnesium tester. Tests every 12 minutes.
- Triton MethodA ULNS reefkeeping protocol from Triton Lab using ICP-testing-driven dosing.
- Two-part dosingLiquid calcium + alkalinity supplementation via dosing pumps.
U
V
Z
Last reviewed