Explainer

How aquaponics
works

Aquaponics combines fish farming (aquaculture) and soilless plant growing (hydroponics) into a single closed-loop system. The fish feed the plants. The plants clean the water. The clean water goes back to the fish. Nothing is wasted. It uses up to 90% less water than conventional farming β€” with no soil, no chemical fertiliser, and no watering schedule.

The aquaponic nitrogen cycle

🐟 Fish tank produces ammonia NH₃ in waste 🦠 Beneficial bacteria NH₃ β†’ NOβ‚‚ β†’ NO₃ Nitrosomonas + Nitrobacter 🌿 Grow beds roots absorb nitrates as plant fertiliser πŸ’§ Clean water returns to fish tank ammonia β†’ β†’ nitrates filtered ← ← clean

The three parts of every system

Fish tank 魚槽

Fish eat, produce waste, and that waste becomes fertiliser. Tilapia and catfish are the most popular beginner choices β€” hardy, fast-growing, and tolerant of a wide pH range. A minimum of 100 gallons gives enough water volume to buffer temperature swings and maintain stable water chemistry.

Beneficial bacteria η‘εŒ–θŒ

Nitrosomonas converts toxic ammonia (NH₃) to nitrite (NOβ‚‚). Nitrobacter converts nitrite to nitrate (NO₃) β€” the form plants absorb. Establishing this colony (called cycling) takes 4–6 weeks when starting a new system. After that the bacteria are self-sustaining, colonising every wet surface in the system.

Grow beds 栽培床

Plants grow with roots in or over the nutrient-rich fish water. They absorb the nitrates β€” feeding themselves while cleaning the water for the fish. No soil, no synthetic fertiliser, no watering schedule. Asian greens, herbs, and leafy vegetables grow especially well because they are heavy nitrogen feeders perfectly matched to the system's output.

Three system types

Media Bed
Gravel or expanded clay fills a bed. Water floods and drains on a timer. Most forgiving system β€” the media acts as biofilter, mechanical filter, and grow medium in one. Best for beginners.
BeginnerHerbs Β· TomatoesLow cost
DWC Raft
A foam board floats on a channel of fish water. Roots dangle freely in the nutrient flow. Highest yield per square foot for leafy greens. Requires separate solids removal before the raft.
IntermediateAsian greensHigh yield
NFT Channel
A thin film of water flows continuously through shallow channels. Very water-efficient. Excellent for herbs and compact crops. More sensitive to pump failures than the other systems.
IntermediateHerbs Β· LettuceWater-efficient

Fish choices

🐟
Tilapia
Hardy, fast-growing, edible. Tolerates pH 6–9. Best all-round beginner fish. Warm water 70–85Β°F.
🐠
Catfish
Excellent waste producers. Tolerates low oxygen better than most fish. Good for warm climates. Edible.
🐑
Koi / Carp
Ornamental option. Strong waste producers. Hardy in cooler water. Beautiful in a backyard system.
🐟
Jade Perch
High omega-3. Best fish for nutrient output per pound of feed. Excellent eating. Warm water species.
Water parameters to monitor weekly

pH 6.8–7.2 is the sweet spot for fish, bacteria, and plants simultaneously. Monitor: ammonia (<1 ppm), nitrite (<1 ppm), nitrate (<80 ppm), dissolved oxygen (>5 mg/L), and temperature. A basic liquid test kit costs around $20 and is essential for the first 3 months.

Design your system β€” free