| Term | Definition |
| A |
| AA | Aquarium Adventure |
| Acro | Acropora (type of sps) |
| Acrylic | A clear plastic material used to construct aquariums. It is half the weight of glass and its refractive index is closer to that of water than glass, making it more transparent. Acrylic is more easily scratched than glass. Also called Plexiglas. |
| Actinic | A type of fluorescent bulb that gives off blue colored light often used in marine aquaria to make corals appear to glow with brilliant colors and to give the tank a "deep ocean" feel to it. |
| Activated Carbon | A Filter Medium used to remove organic contaminants or residual medications from aquarium water. If used it must be renewed at regular intervals. |
| Aerobic | Existing or active in the presence of free oxygen. |
| AGA | All Glass Aquarium |
| Alk | Alkalinity, measure of buffering capacity of water. |
| Alkalinity | The ability of water to maintain a stable pH. Controlled by the amount of carbonate ions present in the water. Also called Buffering Capacity. See KH. |
| Ammonia | An extremely toxic byproduct of fish metabolism and the decay of organic materials. In a fully Cycled tank the ammonia is totally converted to Nitrites and eventually Nitrates by the Bio-Filter. |
| Anaerobic | Existing or active in the absence of free oxygen. |
| Anoxic | Low oxygen. |
| Aquascaping | The artistic arrangement of live rock to create a harmonious and aesthetically pleasing display in an aquarium. |
| Aragonite | A form of calcium carbonate which constitutes the shells of corals and other marine creatures. Crushed Aragonite sand is sometimes used as a Substrate when it is desired to raise the pH/Hardness of the tank water above its natural level, e.g. for African |
| B |
| BB | Bare Bottom (No sandbed) |
| Bio-load | Biological Load. The waste output of organisms that must be processed by the bio-filter. In a balanced system, the bio-load does not exceed the ability of the Bio-filter to process all the waste. See Cycle. |
| Brackish | Slightly salty water typical of river estuaries and lagoons. Some fish, e.g. archer-fish, gobies, and puffers require a brackish aquarium set-up to thrive. |
| BTA | Bubble tip anemone |
| C |
| Ca | Calcium |
| Canister Filter | An external Filter consisting of a sealed canister containing various Filter Media and a pump which circulates water through the media. It is attached to the aquarium by inlet and outlet hoses. |
| Carbon | See Activated Carbon. |
| CFM | Cubic Feet per Minute |
| Chloramine | Combination of Chlorine and Ammonia that is frequently added to municipal water supplies to maintain municipal water quality standards. Also prevents the establishment of Biofilm in municipal water supply lines and storage containers. It is toxic to fish |
| Chlorine | Chemical element that is frequently added to municipal water supplies as a disinfectant. Prevents Biofilm establishment in municipal water supply systems. It is toxic to many fish and inverts. Less stable but a stronger disinfectant than Chloramine, it ca |
| CO2 | Carbon dioxide. Used in Planted Tanks to maximize plant growth. |
| Cycle | 1. v. To establish the nitrogen cycle in an aquatic system by promoting the establishment of nitrifying bacteria. 2. n. The Nitrogen Cycle. |
| D |
| Denitrification | The conversion of Nitrate to nitrogen gas carried out by certain species of bacteria in Anoxic conditions. |
| DI Water | Water that has been purified by deionization. |
| Diatom | Microscopic organism with a hard shell that remains after the death of the organism. |
| Diatom Filter | A Filter which employs the use of diatom powder (the skeletal remains of diatoms). Used to ‘polish’ the water by filtering out particles as small as 1 micron. |
| DIY | Do It Yourself |
| dKH | Degrees of carbonate hardness, measure of alkalinity |
| DSB | Deep Sand Bed |
| F |
| FO | Fish Only. Saltwater aquarium containing fish but not Live Rock or Reef animals. |
| FOWL | Fish Only With Liverock |
| FOWLR | Fish Only With Live Rock (Most people think fowlr in that case) |
| Frag | Fragment; broken or cut piece of coral |
| Fuge (Refugium) | A separate tank which shares water and filtration with the main aquarium. Used for growing Nitrate reducing Algae, raising live food, and isolating inhabitants from the main tank. |
| G |
| GFCI/GFI | Ground fault circuit interrupter / Ground fault interrupter |
| GPH | Gallons Per Hour. The rate at which a filter turns over x amount of Gallons in one hour. |
| Grow Out Tank | A separate tank into which Fry are transferred until they grow to a size suitable for sale, or until they are large enough to be moved back into the aquarium with adults. |
| GSP | Green Star Polyp |
| H |
| Hospital Tank | A separate tank in which sick fish can be isolated from the main tank population while undergoing treatment. See Quarantine Tank. |
| HTH | Hope This Helps/Happy To Help |
| Hybrid | A cross between two or more different species. |
| Hydrometer | An instrument used to measure salinity by Specific Gravity. |
| I |
| Ich | The fish parasite Ichthyophthirius. The main symptom of infection is small white spots on the body of the fish, like grains of salt. Also called White Spot disease. |
| IME/IMO/IMHO | In My Experience/In My Opinion/In My Humble Opinion |
| IMO | In my opinion |
| Inverts | Invertebrates. Animals characterized by a lack of a backbone or internal skeleton. May have an exo-skeleton or shell. |
| IO | Instant Ocean |
| K |
| Kalk | Kalkwasser or Calcium hydroxide |
| KH | Carbonate Hardness. A measurement of the amount of dissolved carbonate and bi-carbonate ions in water. Expressed in degrees of hardness on the German scale (º dH). One degree of hardness equals 17.9 PPM. |
| L |
| LED | Light Emitting Diode |
| LFS | Local Fish Store |
| Live Rock | Calcium carbonate skeletons of corals or other calcareous organisms colonized by beneficial bacteria and micro and macroscopic marine life that live on and inside it. |
| LPS | Large Polyp Stoney Corals |
| LR | Live Rock |
| LS | Live Sand |
| LTA | Long Tentacle Anemone |
| M |
| MH | Metal Halide |
| N |
| Nano Reef | A small Reef Aquarium. |
| Nitrate | The nitrogen compound at the third stage of the Nitrogen Cycle. Nitrate can be used by plants, further processed into nitrogen gas through Anoxic bacterial processes, or reduced by regular partial Water Changes. |
| Nitrite | Intermediate nitrogen compound in the biological conversion of Ammonia to Nitrate in the Nitrogen Cycle. Nitrite is toxic to fish, but less so than Ammonia. |
| Nitrogen Cycle | The natural process (nitrification) by which bacteria convert fish waste and other decaying matter into less harmful compounds. |
| NO | Normal Output |
| O |
| OFL | Online Fish Store |
| P |
| PA | Premium Aquatics |
| PC | Power Compact lighting |
| pH | Measurement of the degree of acidity of water. pH 7 indicates neutral water. Less than 7 is Acidic, and more than 7 is Alkaline. |
| PITA | Pain In The *** |
| PM | Personal or Private Message |
| PPM | Parts per million. |
| Protein Skimmer | Used in saltwater tanks to remove organic pollutants from the water before they break down. Also called Foam Fractionator. Produces tiny air bubbles which attract and hold pollutants, which are then deposited into a separate container. |
| Q |
| Quarantine Tank | A separate tank in which newly acquired fish/coral/ect. are kept for some time to insure that they are not suffering from any disease or parasitic organisims before they are released into the main aquarium. Also used as a Hospital Tank. |
| R |
| RBTA | Rose Bubble Tip Anemone |
| RC | Reef Central (www.reefcentral.com) |
| Refractometer | An instrument used to measure salinity by refraction, the amount light deflects from a straight line through a medium. |
| Refugium (Fuge) | A separate tank which shares water and filtration with the main aquarium. Used for growing Nitrate reducing Algae, raising live food, and isolating inhabitants from the main tank. |
| RO/DI | Reverse Osmosis/De-Ionisation |
| ROFL (LMAO) | Rolls On Floor Laughing (Laughing My *** Off) |
| RR | Reef Ready (Pre-Drilled w/ Overflow) |
| RTN | Rapid Tissue Necrosis |
| S |
| SCWD | Switching Current Water Director, type of wave machine |
| Specific Gravity | A measure of density in comparison to pure water at a specific temperature. In this context, it is used as a measure of Salinity. |
| SPS | Small Polyp Stony Corals |
| T |
| TDS | Total Dissolved Solids |
| V |
| Venturi | A simple device for introducing a gas, e.g. air or CO2, into a water stream in a pipe. |
| VHO | Very High Output |
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