Glossary
Reef hobby glossary
The reef-tank vocabulary, alphabetized. 52 terms, each with a short definition and a link to a deeper reference.
A
- AEFW— Acropora-Eating Flatworm. Pest specific to Acropora corals.
- AI Prime / Hydra— Aqua Illumination LED reef lights. Hydra 32/64 HD are the popular SPS-grade fixtures.
- AIO— All-In-One — a tank with built-in rear filtration chamber instead of an external sump.
- Alkalinity— Water's capacity to neutralize acid. Reported as dKH, meq/L, or ppm CaCO₃.
- Apex (Neptune)— Apex controller from Neptune Systems. Industry-standard reef automation.
- ATO— Auto Top-Off. Adds RODI water to replace evaporation.
B
C
- Calcium— Ca²⁺. Reef target: 410–450 ppm.
- Calcium reactor— Aragonite media chamber that dissolves under CO₂-driven pH 6.5 effluent.
- Carbon dosing— Adding 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.
- Cycling— The 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.
- dKH— Degrees of carbonate hardness — a German alkalinity scale. 1 dKH = 17.86 mg/L CaCO₃ = 0.3566 meq/L.
- DLI— Daily Light Integral. Photons delivered to the substrate per square meter per day.
- DSB— Deep Sand Bed. 4+ inches of fine aragonite for anaerobic denitrification.
F
G
I
K
L
M
N
P
- PAR— Photosynthetically Active Radiation. 400–700 nm. Measured in µmol photons/m²/s.
- pH— Acidity / alkalinity scale. Reef target: 8.1–8.4.
- Phosphate (PO₄³⁻)— Reef target: 0.03–0.08 ppm.
- Protein skimmer— Foam-based mechanical filter that removes organic compounds before they break down.
- PUR— Photosynthetically Usable Radiation. The PAR subset that zooxanthellae pigments actually absorb.
Q
R
S
- Salinity— Total dissolved salt content. Reef target: 35 ppt (SG 1.0264 @ 25 °C).
- Soft corals— Non-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.
- SPS— Small Polyp Stony coral. Acropora, Montipora, Pocillopora, Stylophora.
- Stocking— The fish and inverts inhabiting a tank.
- Sump— Auxiliary tank plumbed below the display for filtration equipment.
T
- Tang police— Hobbyist consensus on minimum tank sizes for tang fish.
- Trident (Neptune)— Automated alkalinity / calcium / magnesium tester. Tests every 12 minutes.
- Triton Method— A ULNS reefkeeping protocol from Triton Lab using ICP-testing-driven dosing.
- Two-part dosing— Liquid calcium + alkalinity supplementation via dosing pumps.
U
V
Z
Last reviewed