hmm. lets see here....
AC...Activated carbon, chemical filtration media / alternating current
AIM...America-On-Line Instant Messenger service
AFAIK...As far as I know
AFM...Aquarium Fish Monthly, magazine
AISI...As I see it
ALK...Alkalinity, measure of buffering capacity of water
AOL...America Online, internet service provider
ASAP...As soon as possible
ATS...Algae turf scrubber, reef setup technique
B4...Before
BOD...Biological oxygen demand
BTW...By the way
Ca...Calcium
CaCl2...Calcium chloride
CaCO3...Calcium carbonate
Ca(OH)2....Calcium hydroxide
CC...Counter current, type of protein skimmer
Cl...Chlorine
CO2...Carbon dioxide
CO3...Carbonate
Cu...Copper
CUL...See you later / catch you later
CUL8R...See you later / catch you later
CYANO...Cyanobacteria
DC...Direct current
DD...Downdraft, type of protein skimmer
DI...Deionisation, type of water purification
DIY...Do it yourself
dKH...Degrees of carbonate hardness, measure of alkalinity
DO...Dissolved oxygen
DOC...Dissolved organic carbon
DSB...Deep Sand Bed
FAMA...Freshwater and Marine Aquaria, magazine
FAQ...Frequently asked question
Fe...Iron
FO...Fish only, type of marine aquarium
FOWLR...Fish Only With Live Rock
FW...Freshwater
FWIW...For what its worth
FYI...For your information
FYM...For your misinformation
GAC...Granular Activated Carbon
GAL...Gallon
GPH...Gallons per hour
HCO3...Hydrogen carbonate
HO...High output fluorescent light
HSA...High speed aeration, type of proteins skimmer
HTH...Hope this helps
I...Iodide
I2...Iodine
ID...Indentify
IE...Internet Explorer, WWW browser
IM...Internet message-AIM,Trillion, Yahoo Messenger, MS messenger
IMCO...In my considered opinion
IME...In my experience
IMEO...In my expert opinion
IMHO...In my humble/honest opinion
IMNSHO...In my not so humble/honest opinion
IMO...In my opinion
IO3...Iodate
IOW...In other words
IR...Infrared, type of light of longer wavelength than visible light
IRC...Internet relay chat
ISP...Internet service provider
JM2C...Just My 2 Cents
JM2CW...Just My 2 Cents Worth
KALK...Kalkwasser, German for calcium hydroxide solution or limewater
KI...Potassium iodide
KISS...Keep it simple stupid
L8R...Later
LFS...Local fish store
LHS...Local hardware store
LOL...Laughing out loud
LPS...Large polyped Scleractinian (stoney) coral; also Local Pet Store
LR...Live rock
LT...Litre
MACNA...Marine Aquaria Conference of North America, held annually
MEQ/L...Milli-equivalents per litre, measure of alkalinity
Mg...Magnesium
MG/L...Milligrams per litre
MH...Metal halide light
MO...Mail order / Money Order
Na...Sodium
NaCO3...Sodium carbonate
NaOH...Sodium hydroxide
NH3...Ammonia
NH4...Ammonium
NNR...Natural nitrate reduction, reef setup technique
NO...Normal output fluorescent light
NO2...Nitrite
NO3...Nitrate
NP...No problem
NRN...No reply necessary
NS...Netscape, WWW browser
NSW...Natural seawater
O2...Oxygen
OBTW...Oh by the way
ORP....Oxidative redox potential
OTOH...On the other hand
PLS...Please
PC...Power compact fluorescent light
pH...Measure of the concentration of hydrogen ions, equal to -log[H+], <7 acidic, =7 neutral, >7 basic
PH...Powerhead, water pump
PM...Private Message
PS...Protein skimmer
PO4...Phosphate
PPM...Parts per million, equivalent to mg/l (milligrams per litre)
PVC...Poly vinyl chloride, used for piping / plumbing
RO...Reverse osmosis, type of water purification
RO/DI...Reverse osmosis, followed by deionisation, type of water purification
ROFL...Rolling on the floor laughing
ROFLOL...Rolling on the floor laughing out loud
ROTFL...Rolling on the floor laughing
ROTFLOL...Rolling on the floor laughing out loud
RTN...Rapid tissue neucrosis
RUGF...Reverse flow undergravel filter
SAL...Salinity
SG...Specific gravity
SHO / T5...Super high output fluorescent light, equivalent to power compact fluorescent
Si...Silicon
SiO2...Silicon dioxide
SITD...Still in the dark
SO...Significant other
SPS...Small polyped Scleractinian (stoney) coral
Sr...Strontium
SSB...Shallow Sand Bed
SW...Saltwater / seawater
TIA...Thanks in advance
TIC...Tongue in cheek
TTYL...Talk to you later
TWP...Tap Water Purifier from Aquatic Pharmaceuticals
TY...Thank You
UGF...Undergravel filter
UV...Ultra violet, type of light of shorter wavelength than visible light
VHO...Very high output fluorescent light
W...Watts
WMC...Western Marine Conference, United States
WWW ...World wide web
WYSIWYG...What you see is what you get
Abbreviation help thread 
