Abbreviations: What do they mean?

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Fighting for the little guy
Nov 29, 2005
I haven't found a topic like this and I'm not sure where to put this one.

Anywhere you go on the Internet People use abbreviations. Anything they can do to shorten typing time. Here is a list of abbreviations I copied from my word document I have saved on my computer. Hopfully it will help.

A: Amp

AC: Activated carbon, chemical filtration media / alternating current

AC: Alternating current

ALK: Alkalinity, measure of buffering capacity of water

ASAP: As soon as possible

ATS: Algae turf scrubber, reef setup technique

B4: Before

BOD: Biological oxygen demand

BR: Base rock

BTA: Bubble tip anemone

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

CR: Calcium reactor

CSD: Carlson surge device

CTA: Cellulose triacetate, type of RO membrane

Cu: Copper

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: Dissolve oxygen

DOC: Dissolved organic carbon

DSB: Deep sand bed

Fe: Iron

FO: Fish only, type of marine aquarium

FOWLR: Fish only with live rock, type of marine aquarium

FW: Freshwater

GAC: Granular activated carbon

GAL: Gallon

GBR: Great Barrier Reef

GPH: Gallons per hour

HCO3: Hydrogen carbonate

HO: High output fluorescent light

HAS: High speed aeration, type of proteins skimmer

I: Iodide

I2: Iodine

ID: Indentify/indetification

IM: In my

IMCO: In my considered opinion

IME: In my experience

IMEO: In my expert opinion

IMO: In my opinion

IO3: Iodate

IR: Infrared, type of light of longer wavelength than visible light

KALK: Kalkwasser, German for calcium hydroxide solution or limewater

KI: Potassium iodide

KISS: Keep it simple stupid

kW: Kilowatt

LFS: Local fish store

LHS: Local hardware store

LPH: Litres per hour

LPS: Large polyped Scleractinian (stoney) coral

LR: Live rock

LS: Live sand

LT: Liter

mA: Milliamp

MEQ/L: Milli-equivalents per litre, measure of alkalinity

Mg: Magnesium

MG/L: Milligrams per litre

MH: Metal halide light

mV: Millivolt

MV: Mercury vapour light

mW: Milliwatt

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

NSW: Natural seawater

O2: Oxygen

OBTW: Oh by the way

ORP: Oxidative redox potential

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

PO4: Phosphate

PPM: Parts per million, equivalent to mg/l (milligrams per litre)

PSI: Pounds per square inch

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

RTN: Rapid tissue neucrosis

RUGF: Reverse flow undergravel filter

SAL: Salinity

SD: Surge device

SG: Specific gravity

SHO: Super high output fluorescent light, equivalent to power compact fluorescent

Si: Silicon

SiO2: Silicon dioxide

SPS: Small polyped Scleractinian (stoney) coral

Sr: Strontium

SW: Saltwater / seawater

TDS: Total dissolved solids

TFC: Thin film composite, type of RO membrane

TWP: Tap Water Purifier

UGF: Undergravel filter

UV: Ultra violet, type of light of shorter wavelength than visible light

V: Volts

VHO: Very high output fluorescent light

W: Watt


No freelancing!
Aug 14, 2001
Real Name
Moving to Discussion on AC, and stickying--though I think we've had a few versions of this and know that Childawg created a website with many of these.

Oh, and adding:

FWIW: For what it's worth

NIMT: Not in my tank!

YMMV: Your mileage may vary


Fighting for the little guy
Nov 29, 2005
I tried to keep the abbreviations I showed more specific to aquariums. My list on my computer is about 12 pages long. I compiled it from my many years on the internet. These were the ones I found right away. It takes awhile to go through 12 pages of abbreviations.


Global Moderator
Aug 27, 2002
Roselle Park, NJ
Real Name
holy shnipes, m.... I don't even know what half of that stuff means :D

at any rate, there is indeed another post somewhere around here with something sort of the same for aquaria etc....

ahhhh.... here it is....


AC Members
Nov 17, 2005
BGK, Black Ghost Knife.
X knife IE clown Royal etc..


Senior padder
Oct 3, 2006
ST.L area
Bump (or punt, or UP or...) means adding a post to a thread solely for the purpose of moving it up to the first page of threads - to bring it from the relative obscurity of later pages to the forefront of everyone's attention. If done too often, it can be very annoying. This applies to any forum.


www.centralcoastreefclub. com
Oct 3, 2005
DOC: Dissolved organic carbon

No.. It means Dissolved Organic Compounds .. ie.. disolved fish poo that floats at the top of the surface.

Talk about a serious bump.. ;) A year and a half since last post?
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