AC - alternating current (electricity)
AGA - All-Glass Aquarium, Aquarium manufacturer
BOD -Biological oxygen demand
CC - Counter current, generally referring to the flow direction in a protein skimmer
CSL - Custom Sea Life, lighting manufacturer
CTA - Cellulose triacetate, type of RO membrane
Cyano - Cyanobacteria
DC - direct current (electricity)
DD - Downdraft, generally referring to the flow direction in a protein skimmer
DI - Deionisation, type of water purification
DIY - Do It Yourself
DSB - Deep Sand Bed
F&S - Drs. Foster and Smith
FO - Fish only
FOWLR - Fish only with live rock
FW - Freshwater
GBR - Great Barrier Reef
GPH - Gallons per hour
HD - Home Depot
HO - High output fluorescent light
HQI - Mercury (Hg) Quartz Iodide, a type of metal halide lamp
IME - In My Experience/Estimation
IMHO - In My Humble/Honest Opinion
IMO - In My Opinion
IO - Instant Ocean, brand of aquarium salt
IR - Infrared
Kalk - aka Kalkwasser, German for calcium hydroxide solution or limewater
LFS - Local fish store
LHS - Local hardware store
LPS - Large polyped Scleractinian (stoney) coral
LR - Live rock
LS - Live sand
MACNA - Marine Aquaria Conference of North America, held annually
MH - Metal halide light
MJ - Maxijet, powerhead manufacturer
MM - Miracle Mud, method of aquarium filtration
MO - Mail order
NO - Normal output fluorescent light
NSW - Natural SeaWater
PC - Power compact fluorescent light
PH - Powerhead, water pump
PVC - Poly vinyl chloride, used for piping / plumbing
RC - Reef Crystals, brand of aquarium salt
RO - Reverse osmosis, type of water purification
RO/DI - Reverse osmosis, followed by deionisation, type of water purification
RR - Reef ready, aquaria with pre-drilled holes and overflows
SG - Specific gravity
SPS - Small polyped Scleractinian (stoney) coral
SW - SaltWater / SeaWater
TFC - Thin film composite, type of RO membrane
UGF - UnderGravel Filter
UV - Ultra violet light
VHO - Very High Output fluorescent light
W/D - Wet-dry (a method of aquarium filtration)
WD - Wet-dry (a method of aquarium filtration)