I'd like to appeal to you  - Please reference the actual definition the first time you use it.

BSA - Biological Surface Area
BSF - Black Soldier Fly
BODBiological oxygen demand
CFCompact fluorescent
CFContinuous Flow
CF – Conductivity Factor
CFL - Compact Fluorescent Lamps
CHIFT PIST - Constant Height In Fish Tank, Pump In Sump Tank
CHOP - Constant Height One Pump
CSA - Community Supported Agriculture
CMH - Ceramic Metal Halide
DFT - Deep Flow Technique
DI - Deionisation
DODissolved oxygen
DOCDissolved organic compounds
DWCDeep water culture
E&Ebb and flow (In ebb and flow the water has to drain back down through the pump)
F&Flood and drain (the water enter the bed in a different location from where it drains back out)
  • timed flood and drain with a stand pipe with holes and a timer or 
  • siphon flood and drain where the pump runs constant and the bed drains via siphon of some sort. 
  • Further explanation with diagrams 
FCR - Feed Conversion Ratio

FRCFloating raft culture
FT fish tank
GAC - Granulated Activated Carbon/Charcoal
GBGrow beds
GHGeneral Hardness, caused by divalent metal ions, primarily calcium and magnesium
GHGreen house 
HDI - High Intensity Discharge lamp
HLR - Hydraulic Loading Rate 
HPSHigh pressure sodium lighting
IBCIndustrial / International / Intermediate bulk container
IMO - Indigenous MicroOrganisms 1,2 & 3
KHCarbonate Hardness, due to carbonate / bicarbonate ions, and represents the main 'buffering capacity' of the water, i.e. its ability to resist pH changes
L50 – Lethal Concentration 50 usually used for gases in air or in the case of fish concentration in water in ppm. The 50 represents a 50% mortality in test subjects.
LD0Lethal Dose 50 at which 50% of the test subjects died. Is usually stated in mg/kg body weight.
LPS - Low Pressure Sodium 
Meg/L - Millequivalents per liter
MHMetal Halide lighting
NC - Normally Closed (refers to relay contacts) contacts closed when relay has no power applied to relay coil (eg 240v), opens when power on
NFT - Nutrient Film Technique
NH4Ammonium, the ionized form of ammonia
NO - Normally Open (refers to relay contacts) contacts open when relay has no power.
NO3 Nitrate
PAC - Powdered Activated Carbon/Charcoal
PC - Power Compact Lights
pH - acidity or alkalinity of a substance
ppmParts per million
ppt - Parts per thousand (i.e. one gram per 1000g or 1Kg per 1000L)
RASRecirculating Aquaponics System
RO - Reverse Osmosis
SG - Specific Gravity, meaning the salinity (salt) content of your water.
SHO - Super High Output (refers to lighting) 
SLO - Solids Lift Overflow 
TAN - Total Ammonia Nitrogen  --- Ammonia, NH3, and NH4
TBPC - Tri-Based Pelletized Carbon
UGFUnder Gravel Filter
UPS - Uninterpretable Power Supply
UVUltra Violet
VHO - Very High Output (refers to lighting)

C     - Carbon
Ca   - Calcium
Cl   - Chlorine
Cu  - Copper
Fe   - Iron
H    - Hydrogen
K    - Potassium
N    - Nitrogen
Na  - Sodium
Mg - Magnesium
Mn - Manganese
Ni  - Nichel
O   - Oxygen
P   - Phosphorus
S   - Sulfur
Z   - Zinc

GH - General hardness (a measure of the concentration of divalent metal ions such as calcium Ca2+, and magnesium Mg2+)
KH - Carbonate hardness (a measure of the alkalinity)
pH  - "power/potential of hydrogen" (A measure of the concentration of Hydrogen atoms, H+)
Alkalinity - The capacity of water for neutralizing an acid
Acid - The negative logarithm of the concentration of hydronium ions - substance that increases the concentration of hydronium ions (H3O+) in solution
Base - The positive logarithm of the concentration of hydronium ions -substance that can accept hydrogen ions or more generally, donate a pair of valence electrons. A soluble base is referred to as an alkali if it contains and releases hydroxide ions (OH−)
Ion - An atom or molecule in which the total number of electrons is not equal to the total number of protons
Anions  - Negatively charged ions
Cations - Positively charged ions
Chelate - The way ions and molecules bind metal ions to allow the metals to be available to plants as nutrients
Ligand  - That which binds to a central metal atom
Divalent - Forming two bonds with other ions or molecules
Anhydrous - Contains no water

CaCO3   - Calcium carbonate (Chalk,  agricultural lime)
CaOH2   - Calcium hydroxide (also called slaked lime, hydrated lime, pickling lime, builders lime)
NaHCO3  - Sodium bicarbonate (Baking soda)
KHCO3    - Potassium bicarbonate (an ingredient of baking powder, also used in fire extinguishers)
K2CO3     - Potassium carbonate.  (primary component of potash)
KCl          - Potassium chloride (available as water softener)
KOH        - Potassium hydroxide
K2SO4    - Potassium sulfate
HCO3      - Bicarbonate
HCL         - Hydrogen Chloride (forms Hydrochloric acid the aqueous solution of hydrogen chloride)
H2CO3   - Carbonic acid (formed by CO2 and H2O as in club soda, soda water, sparkling water, or seltzer water and acid oceans due to burning fossil fuels)
H2SO4    - Sulfuric acid (Used in acidic drain cleaner, and electrolyte in lead-acid batteries)
HNO3     - Nitric acid
H3PO4    - Phosphoric acid
CO2        - Carbon dioxide
OH −        - Hydroxide (functions as a base)
NH4HCO3 - Ammonium bicarbonate
NH4         - Ammonia
NO2−      - Nitrite
NO3−      - Nitrate
MAP       - Magnesium Ammonium Phosphate Hexahydrates