The Pacific Ocean

Photo is a royalty-free image from Pixabay.

Okay, one more time. If at first you don’t succeed, try try again.

Some years ago, Uninja, with the help of forum members Raggamuffin, Wy Renegade, Swannyson, Skinz78, Tabasco 1, Jordan 3548, fsu1dolfan, Stray40, and Rayzback, prepared a list of acronyms which is a sticky in the beginner forum. ksfulk prepared a more recent list and an article. Links to all of these previous iterations are found at the end.

Last month, after I updated one list, I learned that there were several other lists of acronyms. So, I’ve tried to combine every list of marine acronyms and common other non-marine, forum acronyms that I could find into one list. If you have any suggestions for additions, please add them to the comments.


Anoxic, Chiller, Flashing, Frag, Running Carbon, Softies… if any of that sounded confusing to you, we’re here to help. We’ve put together a lovely little (big) list of commonly used slang terms within the community of salt water/marine aquarists so you can master the vocabulary bandied about in our articles and forums and spice up your conversations with other aquarium enthusiasts. You can sound like a big shot.


For the sake of convenience, we’ve placed them in alphabetical order.



1. .02: My two cents.

2. $10: How much anything costs if your spouse asks.


1. A: Amp, Ampere, a measure of electric current.

2. AA: Amino Acid.

3. ABT: Atlantic Blue Tang.

4. AC: Activated Carbon (a chemical filtration medium) or Alternating Current.

5. Acan Lord: Acanthastrea coral, scientific name: Micromussa lordhowensis.

6. Acclimation (Acclimate): The process of a marine lifeform getting accustomed to captive life and your aquarium.

7. Acro: Acropora coral.

8. AEFW: Acropora-eating Flatworms.

9. AGA: All-Glass Aquarium (a brand of aquariums).

10. Aggressive Fish: A fish with a temperament that makes it difficult to have in a community tank.

11. AIO: All-in-One, a prebuilt system that includes pump and filtration.

12. Algae Reactor: A media reactor filled with macroalgae (generally Chaetomorpha) and wrapped in LED lights in order to speed growth and nutrient removal. This is essentially a type of refugium.

13. Alk: Alkalinity, a measure of bicarbonate (HCO3) and carbonate (CO3) in solution, providing the buffering capacity of (salt)water.

14. Anoxic: Used to refer to an area in a tank that’s low on oxygen.

15. Antihelmintic: A drug used for the treatment of parasites and worms (helminths.)

16. Apex: A popular aquarium controller made by Neptune Systems.

17. Aquascape: A contraction of aquarium landscape. Refers to the overall physical design and layout.

18. Aquacultured: A coral/fish that has been grown in captivity, rather than in the wild.

19. Artificial Rock: Can also be Homemade Rock. Refers to man-made shaped materials to act like live rock. Often short on algae, bacteria and pods as they will only acquire transferrable organisms.

20. Assertive Fish: Another fish group. This fish can establish a territory that it will defend but it will also feed well with other fish.

21. ASW: Artificial sea water.

22. ATC: Automatic Temperature Compensation.

23. ATO: Auto Top-Off, a system that automatically adds water lost during evaporation.

24. ATS: Algal Turf Scrubber, a method of removing undesirable nutrients. Also a registered trademark for Hydromentia, Inc.

25. Aussie: Slang for coral gathered in Australian waters.

26. AWC: Automatic water change.


1. BA: Bubble algae, Valonia ventricosa.

2. Base Rock: A meaningless term frequently used by sellers to refer to dead rock. Aquarists often need to ask what this term refers to.

3. B2B: Business to business.

4. B2C: Business to consumer.

5. BB: Bare Bottom, a tank without sand or other substrate.

6. BBT: See above.

7. BC:

8. BCS: Banded Coral Shrimp

9. Bean / BeanAnimal: A drain set up with three stand pipes, one at full siphon, one open channel and an emergency drain, named after its hobbyist originator and known for its near-silent operation.

10. Berlin System: A filtration technique developed in Berlin. Uses live rock, powerful water circulation and strong skimming.

11. Big 3: Refers to common parameters of a reef tank: calcium, alkalinity & magnesium.

12. Biofilter: Refers to the bacteria that convert ammonia into nitrite/nitrate/nitrogen in the aquarium.

13. Bioload: The biological impact placed onto the marine system or the amount of life within a system. Includes, for example, the oxygen needs and wastes produced by fish in your tank.

14. Biological Filtration: Refers to the nitrifying bacteria within an aquarium that break down waste into less harmful by products. Can also refer to macroalgae filtration, deep sand beds, carbon dosing and/or biopellets.

15. BioWheel: A rotating cylinder of filter media that is designed to host bacteria and is often a part of a hang-on-back filter assembly.

16. Blasto: Blastomussa, a genus of large polyp stony corals. Some members of this genus are sometimes found in reef aquariums.

17. BLC: Blue Legged Hermit Crab.

18. Bleaching: Refers to the loss of symbiotic algae (zooxanthellae) in corals leaving them looking bleach-white. Coral bleaching can be triggered by high- or sudden increases in light intensity and elevated water temperatures. High nutrient levels may make some corals more vulnerable to bleaching.

19. BmL: BuildMyLed (once an aquarium LED manufacturer).

20. BoB: Breakout Box (Apex-specific). Used for connecting external switch inputs.

21. BOD: Biological Oxygen Demand. Amount of dissolved oxygen needed in the water for your system.

22. BOGO: Buy One, Get One (Free). A term used in sales of livestock and other products.

23. Bonded Pair: Refers to a pair of fish that have paired off into a male/female pair. These may not yet be of breeding age.

24. BPS: Bubbles Per Second. A term used to describe the amount/rate of CO2 entering a calcium reactor or planted tank.

25. BR: Base Rock (dead rock).

26. Brackish: Brackish Water has more salinity than freshwater but less than seawater.

27. BRB: Be right back.

28. BRS: Bulk Reef Supply (online store and one of our sponsors).

29. BTA: Bubble-Tip Anemone (e.g. Entacmaea quadricolor).

30. BTU: British Thermal Unit.

31. BTW: By the way.


1. Ca: Calcium.

2. CaCl2: Calcium Chloride.

3. Cali: California.

4. CaCO3: Calcium Carbonate.

5. Ca(OH)2: Calcium Hydroxide.

6. Calcium Reactor: Used to create a balance of alkalinity in the system.

7. CaRx: Calcium Reactor.

8. C2C: A coast-to-coast overflow reef aquarium system.

9. CB: Cornbred a well-known coral vendor/propagator.

10. CBB: Copperband Butterflyfish.

11. CC: Counter Current (a type of protein skimmer) or Crushed Coral.

12. CCW: Counter Clockwise.

13. CF: Canister Filter.

14. CFL: Compact Fluorescent Lamp (or Light).

15. CH: Carbonate Hardness (also KH).

16. Chaeto: Chaetomorpha, a macroalgae, sometimes misspelled “Cheato.”

17. Chiller: A piece of equipment used to cool down the water in an aquarium. Equipment that removes heat from the water either by vapor compression or absorption refrigeration.

18. CL: Closed Loop or Craigslist.

19. Closed Loop: An in-tank circulation (flow) approach using an external pump and plumbing in which all components are connected to each other with no other openings (intake and return) other than the aquarium.

20. CO2: Carbon dioxide.

21. COB: Chip On Board, often used to describe a type of LED construction.

22. Colony: An aggregate of individual organisms, generally used to refer to a number of coral polyps.

23. Commensalist Guest: An organism that is hosted or nourished by another organism in a symbiotic relationship.

24. Community Tank: An aquarium populated with fish of several different species.

25. Conductivity: A measure of a solution’s ability to conduct electricity. Generally used as a fast and reliable way to measure the ionic content in the solution. The conductivity of reef tank water is not equal to the salinity of the same water.

26. Cooking: Typically a slang term used to describe a method of soaking rock to leach off (or to remove dead/dying biological tissues by bacteria) any unwanted or undesirable compounds (such as Phosphates), dead tissue or detritus. It generally does not refer to literally cooking rocks.

27. Coralivores: Any organism that feeds on corals.

28. CP: Chloroquine phosphate, a medication used to treat marine ich and marine velvet. It has anti-malarial and anti-inflammatory properties and is an amebicide. Requires a prescription.

29. Crypto: Shorthand for Cryptocaryon irritans (Marine Ich). See Ich.

30. Cu: Copper.

31. CUC: Clean-up Crew. Marine life forms introduced into a marine system that perform ancillary functions.

32. Curing Live Rock: The process of getting rid of decomposing and dead organic materials in and on live rock.

33. CW: Cold Water or Clockwise.

34. CWC: Continuous Water Change.

35. Cyanide Fishing: A destructive fishing technique in which sodium cyanide or some other cyanide compound is used to stun and capture coral reef fish.

36. Cyano: Cyanobacteria. Cyanobacteria are a group of photosynthetic, nitrogen-fixing bacteria that live in a wide variety of moist soils and water.

37. Cycle: Typically refers to establishing the nitrogen cycle in conjunction with starting a new aquarium. We establish the nitrogen cycle, not end it.

38. Cycling: The process of establishing biological filtration in an aquatic system by promoting the growth of nitrifying bacteria.


1. DC: Direct Current.

2. DD: Downdraft, a type of protein skimmer.

3. DD: Diver's Den - a specialized subgroup from that sells WYSIWYG items that go through a heightened quarantine and acclimation. Often these are harder to find fish/corals/invertebrates.

4. DE: Double Ended.

5. Detritus: Dead particulate organic material (as opposed to dissolved organic material). It typically includes the bodies or fragments of dead organisms as well as fecal material. Detritus of aquatic ecosystems is organic material suspended in water and piles up on seabed floors.

6. Detritivore: An organism that feeds on dead organic material, detritus.

7. DFS: Drs. Foster and Smith (an online store in the US).

8. DI: Deionization, a type of water purification. Can also refer to deionization resin.

9. DI water: Deionized Water.

10. Digi: Montipora digitata.

11. Dinos: Dinoflagellates.

12. Dirty: Generally referring to high nutrient levels in an aquarium.

13. Dither fish: A fish that doesn’t hide much, eats well and is peaceful and non-competitive with tank mates.

14. DIY: Do It Yourself.

15. dKH: Degrees of Carbonate Hardness, a measurement of Alkalinity.

16. DO: Dissolved Oxygen.

17. DOC: Dissolved Organic Carbon or Compound.

18. DOM: Dissolved Organic Matter.

19. Dory: Reference to the Disney movie “Finding Nemo”, Dory is a Paracanthurus hepatus, commonly called a hippo tang, blue tang, or palette surgeonfish.

20. Dosing Pump: A controllable pump used to add precise measures (or doses) of water or trace elements or anything to an aquarium at specified intervals.

21. Drip Loop: A cord arrangement set up so that any water that gets on the electrical cord will drip off of the cord rather than running into an electrical outlet.

22. DSB: Deep Sand Bed.

23. DT: Display Tank (your main tank).

24. Durso: A type of drain system featuring a single standpipe drain often constructed to look like a vertically-elongated lowercase “r.” Used in the overflow chamber of older-style “reef ready” tanks, the Durso standpipe ran much quieter than previous, simple upright and open standpipes. The Durso standpipe design was named after its originator, Richard Durso. A radially-symmetric variation of the Durso standpipe, called the Stockman standpipe, was invented by Ken Stockman.


1. EB: Electronic Ballast.

2. EC: End Cap.

3. ESV: A commonly used brand of Alkalinity and Calcium supplement.

4. ETA: Estimated Time of Arrival.

5. Eurobrace: A glass or acrylic brace that is attached to or built into the top of an aquarium to structurally reinforce the vertical panels to keep them from bowing outward from water pressure.


1. FAQ: Frequently Asked Questions.

2. FB: Facebook.

3. Fe: Iron.

4. Feeler: A thread where the originator is asking for opinions on a selling price for an item.

5. Fish Stock Limit: The maximum amount of fish that you can keep in a marine system.

6. Flashing: Refers to a marine fish scraping itself against decorations, often flashing the scales on its belly.

7. FO: Fish Only.

8. Foot: Generally a term used with respect to anemones. This is the basal disc, or part that attaches to the rock or substrate. Can also refer to the foot of a clam or other bivalve.

9. FOWLR: Fish Only With Live Rock.

10. Frag: Fragment (a small part of a coral colony removed in order to grow another colony). Can also be used as a verb to describe a method of physically fragmenting a coral as a method of asexual propagation.

11. Fragmentation: Sectioning of a coral into pieces from which a new colony may be grown. Also known as “fragging.”

12. Frag Plug: A piece of ceramic, plastic or stone used in coral propagation. Frags are mounted on frag plugs.

13. Fry: Recently hatched fish.

14. FTS: Full Tank Shot.

15. FTW: For the win.

16. Fuge: See Refugium.

17. FW: Freshwater.

18. FWD: Freshwater Dip.

19. FWE: Flat Worm Exit (a Salifert product).

20. FWIW: For what it’s worth.


1. G: Gallon (ex. 60g or 60G).

2. GAC: Granular Activated Carbon.

3. GBP: Green Button Polyps.

4. GBR: Great Barrier Reef.

5. GBTA: Green Bubble Tip anemone (e.g. Entacmaea quadricolor).

6. GFCI: Ground Fault Circuit Interrupter.

7. GFI: Ground Fault Interrupter.

8. GFO: Granular Ferric Oxide (a phosphate remover.)

9. GH: General Hardness.

10. GHA: Green Hair Algae.

11. Ghost Overflow: A style of overflow that has a minimal footprint inside of the aquarium and a larger overflow box on the exterior of the aquarium that houses the drain standpipes.

12. GPD: Gallons per Day.

13. GPH: Gallons per Hour.

14. Group Buy: Generally a large number of people making a large order at one time to gain some discount or shipping benefit from a vendor.

15. GSM: Gold Stripe Maroon Clownfish.

16. GSP: Green Star Polyps.

17. Guest: See Commensalist Guest.


1. H2O: The chemical formula for water.

2. H2O2: Hydrogen peroxide.

3. HA: Hair algae.

4. HAB: Harmful algae bloom.

5. HSA: High Speed Aeration, a type of protein skimmer.

6. Herbie: A drain system with two standpipes, one at full siphon and the other, an open-channel with a trickle of water running through it. It’s a predecessor of the Bean/BeanAnimal overflow configuration and was named after its originator “Herbie” who frequented another forum at the time this configuration gained in popularity.

7. HID: High Intensity Discharge (lighting).

8. High Light: A generic term generally referring to the amount of lighting a coral needs to survive. High light is subjectively defined as a PAR measurement greater than 300 mmol/m2s.

9. Hitchhiker: A term used for an organism that was introduced to the tank inadvertently, generally with live rock or a coral frag.

10. HITH: Hole in the Head Disease.

11. HLLE: Head and Lateral Line Disease.

12. HO: High Output (fluorescent lighting).

13. HOB: Hang-On-Back (usually refers to a filter or protein skimmer).

14. HOG: Hang On Glass, a registered trademark for Santa Monica Filtration and type of algae scrubber.

15. Host: An organism that harbors a parasitic, a mutual, or a commensal symbiont, typically providing nourishment and shelter. Example: Anemones hosting clownfish.

16. Hosting: The act of harboring a guest, generally to the mutual benefit of both the Guest and the Host. Example: Anemones hosting a clownfish.

17. HOT: Hang-on-Tank or Hang-on-Top.

18. HSA: High Speed Aeration, a type of protein skimmer.

19. HT: Hospital Tank.

20. HTH: (I) hope that helps.

21. HQI: Hardest Question Is or can refer to a Mercury (Hg) Quartz Iodide lamp, a subset of the family of HID lamps.

22. HWMBO: He who must be obeyed.

23. Hydrometer: A device used to measure the specific gravity of seawater.

24. Hypoxia: Lacking or deficient in oxygen.


1. I/I2: Iodide, Iodine.

2. Ich or Ick: Cryptocaryon irritans is a species of ciliates that parasitizes marine fish, causing marine white spot disease or marine ich.

3. ICP: Abbreviation for Inductive Coupled Plasma. Typically shorthand for ICP-OES (Optical Emission Spectrometry), a type of spectrometry capable of detecting the chemical element components of a test sample. This is achieved by ionizing the sample with inductively coupled plasma, and analyzing the optical spectral lines resulting from the process.

4. IDK: I don’t know.

5. IME: In my experience.

6. IMHO: In my humble opinion.

7. IMO: In my opinion.

8. IO: Instant Ocean (a brand of aquarium salt).

9. IR: Infrared.

10. IW: In Wall.


1. JF: Jason Fox, a well-known coral vendor/propagator.


1. K: Kelvin.

2. Kalk: Kalkwasser, German for a saturated calcium hydroxide solution or limewater, a common reef aquarium additive for calcium and reef building.

3. KISS: Keep it simple, stupid.

4. KMNO4: Potassium permanganate, a chemical used for disinfection of equipment and for fish baths and swabs. A powerful oxidizer. Will kill snails, snail eggs and some parasites depending on strength of solution. Use with extreme caution. It is neutralized with hydrogen peroxide, H2O2.

5. kWh or kWhr: Kilowatt Hour.


1. L: Liter.

2. LA: LiveAquaria(.com)

3. lb: pound.

4. LED: Light Emitting Diodes.

5. Lepto: Leptoseris coral.

6. LFS: Local Fish Store (or pet store selling fish and fish supplies).

7. LHS: Local Hardware Store.

8. Live rock: Rocks removed from the ocean (wild) or artificially farmed that usually have a variety of sea life attached to them. Can also be rock that is colonized by bacteria for use as part of a biological filter in an aquarium.

9. LMB: Lawnmower Blenny.

10. LMK: Let me know.

11. LNS: Low Nutrient System.

12. Lobo: Lobophyllia. Commonly called lobed brain coral or lobo coral, this is a genus of large polyp stony corals (LPS).

13. LOL or lol: Laugh out loud.

14. Low Light: A generic term generally referring to the amount of lighting a coral needs to survive. Low light is subjectively defined as a PAR measurement of 100 (mmol/m2s .) or less.

15. LPD/H/M: Liters per Day/Hour/Minute.

16. LPS: Large Polyp Stony coral.

17. LR: Live Rock.

18. LS: Live Sand.

19. LTA: Long Tentacle Anemone.

20. LX or Lux: Amount of lighting (one lumen) per square meter.

21. Lymph: Short for Lymphocystis, a common viral infection in marine fish.


1. MACNA: Marine Aquaria Conference of North America.

2. Macro or Macroalgae: This typically refers to algae that form larger and complex growth forms like Chaetomorpha.

3. Maricultured: Typically refers to coral that has been grown or farmed in the ocean.

4. Marine ich: See Ich.

5. Marine System: Refers to the entire tank construction and all equipment for it.

6. Marine velvet: Velvet disease, also called gold dust disease, is a fish disease caused by dinoflagellate parasites of the genus Piscinoodinium, which gives the fish a dusty, slimy look.

7. Marine White Spot Disease: See Ich.

8. MASNA: Marine Aquarium Societies of North America.

9. Mag: Magnesium (chemical symbol Mg); can also refer to a series of pumps made by Danner (e.g. Mag-7).

10. MB: Magnetic ballast.

11. MD: MarineDepot(.com)

12. Mechanical filtration: A method of capturing floating debris from the aquarium water and removing it before it breaks down further. Generally filter socks and filter pads are used.

13. Media: Purposefully placed solid material in the marine system often for filtering purposes.

14. mEq/L: Milliequivalents per Liter (a milliequivalent is 1/1000 of an equivalent). Typically seen in the hobby associated with alkalinity measurements. 1 mEq/L = 2.8 dKH = 50 ppm as CaCO3.

15. Mg: Magnesium.

16. mg: Milligram.

17. mg/L: Milligrams per Liter.

18. MH: Metal Halide (Light).

19. Milli: Acropora Millipora.

20. Mini-Cycle: See Cycle.

21. Mini Nem: Short for Mini Carpet Anemone.

22. Mixed Reef: Generally refers to an aquarium that contains a combination of SPS, LPS and Soft corals.

23. MJ: Maxijet.

24. MM: Miracle Mud, a type of substrate for freshwater and saltwater aquariums.

25. Mr. Saltwater Tank: Mark Callahan, a YouTube personality with a web series devoted to the reefing hobby.

26. MS: Mass Spectrometry.

27. MTS: Multiple Tank Syndrome. When you can’t stop adding more tanks and more fish ad nauseum. Very serious affliction with high degree of contagion among reef aquarists.

28. MV: Mercury Vapor.

29. Mysis: A small freshwater shrimp widely used as frozen food for marine aquariums.


1. N2: Nitrogen (gas).

2. Na: Sodium.

3. Na2CO3: Sodium carbonate (soda ash).

4. NaHCO3: Sodium bicarbonate (baking soda).

5. Nano Tank: A small aquarium, generally between 5 and 20 gallons in size.

6. NAOH: Sodium hydroxide.

7. Necrosis: Cell death caused by unplanned cellular injury.

8. Nemo: A reference to the Disney movie “Finding Nemo”; Nemo is an Amphiprion ocellaris, commonly called a clownfish.

9. Nems: anemones.

10. Newb or Newbie: A person new to the hobby.

11. NH3: Ammonia.

12. NH4: Ammonium, a positively charged ion of ammonia.

13. Nitrification: The process by which ammonia is changed into nitrite, then nitrate then nitrogen gas.

14. nm: Nanometer, a measurement often used in lighting terminology.

15. NNR: Natural Nitrate Reduction.

16. NO: Normal Output (fluorescent light).

17. NO2: Nitrite.

18. NO3: Nitrate.

19. NOPOX: NO3PO4X is a Red Sea additive used for controlling nutrients.

20. NPS: Non-Photosynthetic.

21. NRN: No reply necessary.

22. NSL: Natural Sunlight.

23. NSW: Natural Seawater.

24. NTS: New Tank Syndrome. May be caused by lack of beneficial bacteria and/or increasing bio-load too fast, and/or overzealous cleaning of equipment.


1. O2: Oxygen.

2. OC: Original collector.

3. OC: Open channel. A drain tube that allows both water and air to enter.

4. One Inch Per Gallon: An antiquated adage that a certain total inches of fish would be compatible with the total gallon size in an aquarium. This ‘rule’ is widely believed to be incorrect.

5. ORA: Oceans, Reefs, and Aquariums.

6. ORP: Oxidation Reduction Potential.

7. OTS: Old tank syndrome.


1. PA: Premium Aquatics.

2. Paly: Palythoa.

3. PAR: Photosynthetically Active Radiation.

4. PAS: Photosynthetic Action Spectrum.

5. Pathogenesis: The origin of a disease.

6. PB: Pulse Ballast.

7. PBT: Powder Blue Tang.

8. PC: Power Compact.

9. PE: Polyp Extension (in relation to coral).

10. PE: Piscine Energetics (food company).

11. pH: Logarithmic measure of the concentration of hydrogen Ions (hydronium) used to measure acidity. Its value is equal to -log(H+). pH values <7 are considered acidic. pH values >7 are considered alkaline or basic. A pH value of 7 is considered neutral. Typical pH range in a reef tank is 7.8 – 8.2.

12. PH: Powerhead.

13. Phosphate: A nutrient that can cause uncontrolled algae growth.

14. Photoperiod: The length of time each day that the aquarium lights remain on.

15. Pico Tank: A small aquarium, generally less than five gallons in size.

16. Piping: When a fish goes to the surface to gulp air. Usually an important indicator of water oxygen levels.

17. PM: Private message (through the forum).

18. PO4: Phosphate.

19. Pods: Refers to a variety of small crustaceans, usually copepods and amphipods.

20. POTM: Picture of the month.

21. PP: per polyp or Potassium permanganate (see KMNO4).

22. PPM: Parts Per Million.

23. PPT: Parts Per Thousand.

24. Prazi: short for Prazipro, a commonly used antihelmintic, deworming medication.

25. Profilux: A popular aquarium controller made by GHL.

26. PUR: Photosyntheically Usable Radiation, a unit associated with light measurement.

27. PS: Protein Skimmer.

28. PVC: Polyvinyl Chloride.


1. QM: Quality Marine.

2. QT: Quarantine Tank, used before introducing new livestock to display tank.


1. R2R:

2. RAP: Reef-A-Palooza, a large reefing conference.

3. RB: Reef Brite LED.

4. RBTA: Rose Bubble-Tip Anemone (sp. Entacmaea quadricolor).

5. RC: Reef Crystals or Reef Central.

6. RDSB: Remote Deep Sand Bed.

7. Redfield Ratio: The atomic ratio of carbon, nitrogen and phosphorus found in phytoplankton and throughout the deep oceans. This empirically developed stoichiometric ratio was originally found to be C : N : P = 117:14:1.

8. Reflector: Something having a polished surface for reflecting light.

9. Refugium: An area separate from the main tank that’s meant to be a refuge and habitat free from predation, often used for the growth of macroalgae and copepods, and sometimes on a light cycle that is the opposite of the display tank.

10. Reverse-flow Filtration: A Biological Filtration System where water is returned to the aquarium at the base rather than the water’s surface.

11. RHF: Randy Holmes-Farley, R2R’s resident chemist with his own forum.

12. Rics: Ricordia.

13. Rimless: An aquarium that has no plastic or eurobracing around the top of the tank.

14. RIP: Rest in peace.

15. RK/RKL: ReefKeeper/ReefKeeper Lite, a popular aquarium controller.

16. RO: Reverse Osmosis, a type of water purification routinely used for saltwater aquariums.

17. RO Water: Reverse Osmosis Water.

18. RODI or RO/DI: Reverse Osmosis and Deionization (unit or water that has passed through this unit.) By the way, it’s not recommended to drink RODI water, not least because the resin is not food grade.

19. ROTFLMBO: Roll on the floor laughing my butt off. Sometimes ROFL for roll on the floor laughing.

20. ROX: A specific type of activated carbon used to remove impurities from the water. Generally considered an aggressive type of carbon.

21. RP: Return Pump.

22. RR: Reef Ready, aquaria with one or more overflows and predrilled holes for plumbing to a sump.

23. RR: Reef Raft (corals).

24. RSP: Red sea pro salt.

25. RTN: Rapid Tissue Necrosis.

26. RUGF: Reverse Flow Under-Gravel Filter.

27. Running Carbon: Using carbon filtration in your tank.


1. SAL: Salinity.

2. Sanjay: Refers to Sanjay Joshi, a well-known authority on reef lighting.

3. SE: Single Ended.

4. SG: Specific Gravity. A ratio of density.

5. SHO/T5: Super High Output Fluorescent Light, equivalent to power compact fluorescents.

6. Shrooms: Mushroom Coral.

7. Shy Fish: A fish that tends to hide, not swim in the open and not compete for food, especially when housed with more assertive fish, which can be problematic and lead to fish death.

8. Si: Silicon.

9. SiO2: Silicon Dioxide.

10. SLR: Single Light Reflector.

11. SMH: Shake my head.

12. Socks: Refers to filter socks, a type of mechanical filtration.

13. Softy: Corals that lack a rigid calcium skeleton. Typically zoanthids, mushrooms, leathers and xenias.

14. SPS: Small Polyp Stony Coral.

15. SSB: Shallow Sand Bed.

16. Starphire: A brand of low-iron ultra-clear glass made by Vitro Architectural Glass..

17. STN: Slow Tissue Necrosis.

18. Stoichiometry: The calculation of relative quantities of reactants and products in chemical reactions.

19. Sump: A container linked to the aquarium that typically houses equipment like wet/dry filters, skimmers, heaters, dosers, and sometimes refugiums. Sumps add to the overall volume of water in your system.

20. SW: Saltwater or Sea Water.

21. SWMBO: She who must be obeyed.


1. T5/T8: Types (sizes) of fluorescent lighting. The number refers to the diameter of the lamp tube in eighths of an inch. Thus, T5 lamps are 5/8 inch in diameter and T8 lamps are 8/8 or 1 inch in diameter.

2. Tank: An aquarium.

3. Tank Hopping: Moving a fish from a display tank to a larger display tank when that fish gets too large.

4. TBS: Tampa Bay Saltwater (.com)

5. TDS: Total Dissolved Solids.

6. Texas Trash: See Green Button Polyps. An often considered undesirable and invasive coral.

7. TFC: Thin Film Composite, a type of RO membrane.

8. TIA: Thanks in Advance.

9. TIC: Total Inorganic Carbon.

10. TL;DR: Too long didn’t read.

11. TLTR: Too long to read.

12. TM: Temperature.

13. TMI: Too Much Information.

14. Tort: Acropora tortuosa.

15. TOTM: Tank of the Month.

16. Trachy: Trachyphyllia.

17. Triton Test: An ICP-OES analysis (See ICP). A sample of aquarium water is mailed to the testing lab and results are generally available online in 7-10 days.

18. TTM: Tank Transfer Method. A method of quarantining fish to prevent and cure Cryptocaryon irritans, marine ich. See Ich. This method is not effective at treating any other fish disease (as far as we know at this time.)

19. Turnover: The rate of water leaving and re-entering the aquarium or the total of the rate of water leaving and re-entering the aquarium added to the amount of water moving around inside the aquarium by pumps or powerheads.

20. Two Part: Refers to an additive system using 2 or more components to supplement calcium and alkalinity. One can often supplement magnesium as a “third” part.

21. Tyree: Named after Steve Tyree, a well-known coral vendor/propagator.

22. TYT: Take your time.


1. UAS: Upflow algae scrubber.

2. UGF: Under-Gravel Filter.

3. ULNS: Ultra-Low Nutrient System.

4. UPS: Uninterruptible Power Supply.

5. UV: Ultraviolet, a type of light that is shorter wavelength than visible light (but longer than X-rays), sometimes broken down into UVA, UVB, and UVC.


1. V: Volt.

2. VHO: Very High Output (fluorescent light).

3. VSV: Vodka, Sugar and/or Vinegar.


1. W: Watts.

2. Water Change: The process of removing old aquarium water and replacing it with new water.

3. WC: Water Change.

4. WD: Wet-Dry, a type of filtration. Can also refer to Walt Disney, a “named” acro.

5. Wellso: Wellsophyllia.

6. WPG: Watts per Gallon, an outdated rule of thumb pertaining to lighting requirements that is, today, considered an invalid oversimplification.

7. WQ: Water quality.

8. WTB: Want to Buy.

9. WTS: Want to Sell.

10. WTT: Want to Trade.

11. WWC: World Wide Corals.

12. WYSIWYG: What you see is what you get.


1. XHO: Extra high output light.


1. YGPM: You’ve got a private message.

2. YOLO: You only live once.

3. YWG: Yellow Watchman Goby or Yellow Prawn Goby (Cryptocentrus cinctus.)

A Yellow Watchman Goby or Yellow Prawn Goby

Photo is from the Reef2Reef archives courtesy of ©2018, All Rights Reserved.


1. Z&P: Zoanthid and Palythoa.

2. Zoa: Zoanthid.

3. Zoos: slang for Zoanthids.

While there may be as wide a selection of slang terms as there are fish in the sea with this article, we hope that we have armed you well with a varied vocabulary to integrate into your arsenal of aquarist knowledge.


Note from the Editor:

Conspicuously absent from this list are any acronyms that contain vulgarity or masked vulgarity or even possibly suggested vulgarity because they are not permitted on Reef2Reef. We are a family-friendly forum.

This list was prepared not just from previously published lists credited to the people in the second paragraph above, but also with the significant help from Peter Steckley, a technical writer based in Calgary.

A special thanks is due today to the following individuals: Tom Land, President Emeritus of the Washington DC Area Marine Aquarist Society (WAMAS), for reading, editing, and proofreading this list more times than I’d like to admit. He provided advice, definitions, additions, and corrections and is always pleasure to work with.


We encourage all our readers to join the Reef2Reef forum. It’s easy to register, free, and reefkeeping is much easier and more fun in a community of fellow aquarists. We pride ourselves on a warm and family-friendly forum where everyone is welcome. You will also find lots of contests and giveaways from our sponsors.



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