Aquaponics Final Exam Practice – Solved MCQs
(100 Questions, Answers, and Rationales)
1. What is the primary function of the biofilter in an aquaponic
system?
A. Remove solid waste
B. Convert ammonia to nitrate
C. Oxygenate the water
D. Reduce water temperature
Rationale: Biofilters house nitrifying bacteria that convert toxic
ammonia into plant-usable nitrate.
2. Which organism produces the ammonia needed for nitrification?
A. Plants
B. Fish
C. Earthworms
D. Fungi
Rationale: Fish excrete ammonia through their gills and urine, fueling
the nitrogen cycle.
3. Which bacteria convert nitrite to nitrate?
A. E. coli
B. Rhizobium
C. Nitrobacter
D. Cyanobacteria
Rationale: Nitrobacter complete the second stage of nitrification,
forming nitrate from nitrite.
4. What is the ideal pH range for most aquaponic systems?
,A. 4.5–5.5
B. 6.0–6.5
C. 6.8–7.2
D. 7.8–8.5
Rationale: A pH of 6.8–7.2 balances the needs of fish, plants, and
nitrifying bacteria.
5. Which fish species is most commonly used in warm-water
aquaponics?
A. Trout
B. Salmon
C. Tilapia
D. Catfish
Rationale: Tilapia tolerate a wide temperature range and fluctuating
water quality, making them ideal.
6. What is the main purpose of the clarifier (solid separator)?
A. Add oxygen
B. Remove settleable solids
C. Reduce pH
D. Increase temperature
Rationale: Clarifiers remove heavier solids before water reaches the
biofilter.
7. What does dissolved oxygen (DO) primarily support in the system?
A. pH stability
B. Mineralization
C. Fish respiration
D. Nitrate uptake
Rationale: Fish require sufficient DO for healthy respiration.
8. What happens when ammonia levels exceed 1.0 ppm?
, A. Plants grow faster
B. Fish experience toxicity
C. Nitrate production stops
D. Water becomes alkaline
Rationale: Ammonia above 1.0 ppm becomes harmful to fish.
9. Which component helps remove fine suspended solids?
A. Settling tank
B. Grow bed
C. Biofilter
D. Foam fractionator
Rationale: Foam fractionators remove small suspended particles and
dissolved organic compounds.
10. What is chelated iron added for?
A. Fish digestion
B. Plant micronutrient supply
C. Water alkalinity
D. Bacterial growth
Rationale: Chelated iron corrects plant chlorosis and ensures
micronutrient availability.
11. What ratio of fish tank volume to grow bed volume is commonly
recommended?
A. 1:5
B. 1:1
C. 5:1
D. 10:1
Rationale: A balanced 1:1 ratio supports nutrient cycling and water
stability.
(100 Questions, Answers, and Rationales)
1. What is the primary function of the biofilter in an aquaponic
system?
A. Remove solid waste
B. Convert ammonia to nitrate
C. Oxygenate the water
D. Reduce water temperature
Rationale: Biofilters house nitrifying bacteria that convert toxic
ammonia into plant-usable nitrate.
2. Which organism produces the ammonia needed for nitrification?
A. Plants
B. Fish
C. Earthworms
D. Fungi
Rationale: Fish excrete ammonia through their gills and urine, fueling
the nitrogen cycle.
3. Which bacteria convert nitrite to nitrate?
A. E. coli
B. Rhizobium
C. Nitrobacter
D. Cyanobacteria
Rationale: Nitrobacter complete the second stage of nitrification,
forming nitrate from nitrite.
4. What is the ideal pH range for most aquaponic systems?
,A. 4.5–5.5
B. 6.0–6.5
C. 6.8–7.2
D. 7.8–8.5
Rationale: A pH of 6.8–7.2 balances the needs of fish, plants, and
nitrifying bacteria.
5. Which fish species is most commonly used in warm-water
aquaponics?
A. Trout
B. Salmon
C. Tilapia
D. Catfish
Rationale: Tilapia tolerate a wide temperature range and fluctuating
water quality, making them ideal.
6. What is the main purpose of the clarifier (solid separator)?
A. Add oxygen
B. Remove settleable solids
C. Reduce pH
D. Increase temperature
Rationale: Clarifiers remove heavier solids before water reaches the
biofilter.
7. What does dissolved oxygen (DO) primarily support in the system?
A. pH stability
B. Mineralization
C. Fish respiration
D. Nitrate uptake
Rationale: Fish require sufficient DO for healthy respiration.
8. What happens when ammonia levels exceed 1.0 ppm?
, A. Plants grow faster
B. Fish experience toxicity
C. Nitrate production stops
D. Water becomes alkaline
Rationale: Ammonia above 1.0 ppm becomes harmful to fish.
9. Which component helps remove fine suspended solids?
A. Settling tank
B. Grow bed
C. Biofilter
D. Foam fractionator
Rationale: Foam fractionators remove small suspended particles and
dissolved organic compounds.
10. What is chelated iron added for?
A. Fish digestion
B. Plant micronutrient supply
C. Water alkalinity
D. Bacterial growth
Rationale: Chelated iron corrects plant chlorosis and ensures
micronutrient availability.
11. What ratio of fish tank volume to grow bed volume is commonly
recommended?
A. 1:5
B. 1:1
C. 5:1
D. 10:1
Rationale: A balanced 1:1 ratio supports nutrient cycling and water
stability.
