Knowledge Centre
Aquaculture Glossary
Twenty-four terms used throughout this portal, defined plainly. Use the filter to find a term quickly.
Aeration
- The addition of air to water to increase dissolved oxygen and create circulation, using devices such as paddlewheels, diffusers and aspirators.
Alkalinity
- A measure of water's capacity to neutralise acid, mainly from bicarbonate and carbonate. Adequate alkalinity stabilises pH and supports nitrifying bacteria in biofilters.
Ammonia
- A nitrogen compound excreted by fish and released from decomposing feed. Un-ionised ammonia is toxic; biofilters convert it to nitrite and then nitrate.
Aquaponics
- An integrated system in which nutrient-rich water from fish culture feeds soilless plant cultivation, with plants and microbes helping to treat the water.
Biofilter
- A treatment unit providing surface area for nitrifying bacteria that convert ammonia to nitrite and nitrite to nitrate.
Biofloc
- Aggregates of bacteria, algae, protozoa and organic particles maintained in the culture water, which recycle nitrogen and serve as supplementary food for shrimp and some fish.
Biosecurity
- Practices that prevent the introduction and spread of pathogens, including water screening, certified seed, controlled access and dedicated equipment.
Brackish water
- Water with salinity between freshwater and seawater, typical of estuaries and coastal zones, and required by species such as whiteleg shrimp and mud crab.
Broodstock
- Mature fish or shrimp kept for breeding in a hatchery.
Cage culture
- Rearing fish in net enclosures suspended in reservoirs, lakes or coastal waters.
Carbon-to-nitrogen ratio (C:N)
- The balance of carbon and nitrogen available to microbes; raised in biofloc systems by adding carbohydrate so that bacteria take up ammonia.
Denitrification
- The microbial conversion of nitrate to nitrogen gas under low-oxygen conditions, used in some RAS to limit nitrate accumulation.
Dissolved oxygen (DO)
- The amount of oxygen gas dissolved in water, measured in milligrams per litre or percentage saturation; the most critical water-quality parameter in intensive aquaculture.
Drum filter
- A rotating mechanical filter with a fine mesh screen that removes suspended solids from water and backwashes them to a waste stream.
Feed conversion ratio (FCR)
- The weight of feed given divided by the weight gained by the animals; a lower FCR indicates more efficient feeding.
Fingerling
- A young fish that has passed the fry stage and is large enough to stock in grow-out ponds or tanks.
Hatchery
- A facility where broodstock are held and spawned and eggs and larvae are reared under controlled conditions to produce seed.
Nitrite
- An intermediate nitrogen compound produced when bacteria oxidise ammonia; toxic to fish and shrimp, especially during biofilter start-up.
Nitrate
- The end product of nitrification; far less toxic than ammonia or nitrite but accumulates in recirculating systems unless diluted or denitrified.
Nursery
- A protected pond, tank or raceway where fry or post-larvae are grown to a size that survives stocking in grow-out systems.
Post-larvae (PL)
- Young shrimp that have completed their larval stages and resemble miniature adults; the stage at which shrimp are stocked.
Recirculating Aquaculture System (RAS)
- A land-based system that treats and reuses most of its water through mechanical filtration, biofiltration, gas management and conditioning, with a small daily replacement volume.
Sludge
- The concentrated solid waste removed from aquaculture water by filtration or settling, which must be dewatered and managed responsibly.
Specific pathogen free (SPF)
- Broodstock or seed certified free of a defined list of pathogens, produced under biosecure conditions; central to shrimp farming.