sirdarksol

This is a work in progress. Please feel free to add to it. Thanks to Lucy for the list she sent me. It tripled the list I had here.
Also, the fact that these are here does not mean you need to use them. Many of them are already kind of dead (there are two in the list that I've never seen before). I'm not including this so that everyone talks exactly the same, but rather for people to brush up on their aquariumspeak.
Edit: I am editing some of the new answers into my own post. Others, I'm leaving out (though they'll still be in the post further down the list). I'm basing this largely on whether or not they're commonly used on the forum.

DFS = Doctors Foster and Smith A pet supply company.

MTS = Multiple Tank Syndrome A communicable disease which causes aquarists to buy more and more tanks in order to accommodate more fish.

MTS = Malaysian Trumpet Snail You've just got to use context to tell which one a member is referring to.

GBR = German Blue Ram

JD = Jack Dempsey A type of cichlid.

DG = Dwarf Gourami

GSP = green spotted puffer

BN Pleco = Bristle Nose Pleco

CAE = Chinese Algae Eater

SAE = Siamese Algae Eater

HOB = Hang-on-Back A type of filter.

UGF = Under Gravel Filter

WPG = Watts per Gallon A reference to lighting.

GPH = Gallons per Hour A reference to filter/pump power.

LPS = Local Pet Store

LFS = Local Fish Store Not to be confused with a Petsmart, Petco, or Walmart, which are usually referred to by name or as "big chain."

RTS = red tail shark

NTS = New Tank Syndrome More of an old school term, from when less was known about the nitrogen cycle.

FOWLR = Fish Only with live rock A type of marine aquarium.

PWC = Partial water change

RO = reverse osmosis A process that creates nearly pure water.

API = Aquarium Pharmaceuticals Inc Most often used to describe the API Master Testkit.

AC = activated carbon

FW = Freshwater

SW = Saltwater

NH3 = ammonia

NO2 = Nitrites

NO3 =Nitrates

And, some common netspeak

LOL = Laugh Out Loud

ROFL / ROTFL = Rolling on the Floor Laughing

IMO / IMHO = In My (Humble) Opinion

FYI = For Your Information

BTW= By the Way

Red1313

RTS= Red tail shark

Aquarium related only?

jgon_

LFS: local fish store
:P

sirdarksol

Yes. This list is really aimed at the stuff Fishloreans use.

Lucy

NH3 = Ammonia
NO2 = Nitrites
NO3 = Nitrates

MeGustaUnaPez926

DP- dwarf puffer
GSP- Green spotted puffer

Shaina

DFS - DrsFosterSmith.com a popular online pet store
GBR - German Blue Ram Cichlid
BR - Bolivian Ram Cichlid
GT - Green Terror Cichlid
JD - Jack Dempsey Cichlid
BGJD - Blue Gene Jack Dempsey Cichlid heterogeneous recessive gene for blue
EBJD - Electric Blue Jack Demsey Cichlid homozygous for blue
RCS - Red Cherry Shrimp
CRS - Crystal Red Shrimp
BN - Bristlenose Pleco
SA - South American usually refers to species from this area
CA - Central American usually refers to species from this area

Red1313

betta Tail types?
HM = Halfmoon
CT = Crown Tail
OHM = Over Halfmoon
PK = Planket
VT = Veil Tail

One more that threw me off when I first looked at it
ID = Irridecent Shark

Lucy

DIY = Do It Yourself

Mike19

TBH = To Be Honest

pinkfloydpuffer

GSP is on there, so I'm happy

I'm glad we have this, very handy. I had no idea what DG was

dancerhas

I use CAE instead of Chinese Algae Eater all the time.

I've also seen instances of SAE for Siamese Algae Eater

dancerhas

F8 - Figure Eight Puffer?

NaCl

Thank SO much for the list of abreviations, acronyms & lingo. As a newcomer to the forum I had been wondering about some of the abreviations. This is very heplful.

Thanks, sirdarksol.

Sue NaCl

Kayin1470

IDK - I don't know
SHARK - super hungry, aggravated, (and) risky killer. omg it's a SHARK swim away!
FISH - forgivable (and) initially silly, humans. awww ur such a FISH


did I miss any?

sirdarksol

I've got to say that, by this point, the credit has to go to Lucy and the people who posted in the thread. My original list had around ten abbreviations in it. The rest come from everyone else.

angelfish220

I'm such a FISH

CoryMac

CD=CoryDoras
FJ= False Julii