Nitrogen Cycle
What compound is produced first when fish release waste?
Ammonia (NH₃)
What is the safe pH range for most aquaculture species?
About 6.5–8.5
List one visible sign of stress in fish.
Gasping at surface, clamped fins, abnormal swimming, loss of appetite.
What tool moves water and provides oxygen in a tank?
Aerator or air pump.
Define aquaculture.
The farming of aquatic organisms like fish, shellfish, and plants.
What type of bacteria convert ammonia into nitrite?
Nitrosomonas (beneficial bacteria)
What parameter measures dissolved salts in water?
Salinity
What does “ich” look like on fish?
Small white spots, like salt grains
What should you do if ammonia levels are high?
Partial water change, reduce feeding, add bacteria supplement.
What does “monoculture” mean in aquaculture?
Raising one species in a system.
Why is nitrite harmful to fish?
It binds to blood, reducing oxygen transport (“brown blood disease”)
Why is dissolved oxygen (DO) important for fish?
Fish need DO for respiration; low DO can cause stress or death.
How can poor water quality affect fish immune systems?
It weakens them, making them more prone to disease.
Why is overfeeding dangerous?
Uneaten food decomposes, raising ammonia levels.
What is the term for raising fish and plants together in one system?
Aquaponics.
What is the final, less harmful compound in the nitrogen cycle?
Nitrate (NO₃⁻)
What can happen if water temperature rises too high?
Oxygen levels drop, and fish become stressed.
What is a common treatment for bacterial infections in aquaculture?
Antibiotics or medicated feed (when prescribed and regulated).
What is biofiltration?
The use of beneficial bacteria to convert toxic waste products.
Define “stocking density.”
The number of fish kept in a given water volume
Why is tank cycling important before adding fish?
It establishes beneficial bacteria to process waste and prevent toxic spikes.
What tool is commonly used to test ammonia, nitrite, and nitrate levels?
Water testing kit or strips.
Why is quarantine important for new fish?
Prevents introducing diseases into established tanks.
Name one advantage of a recirculating aquaculture system (RAS).
Conserves water, better control of water quality, higher fish density possible
What is the process of preparing a tank by establishing beneficial bacteria before adding fish?
Cycling (or Tank Cycling).