Aquaponics combines fish farming with soil-free plant growing. Fish live in tanks, and their nutrient-rich water is pumped to beds and pipes planted with vegetables. Beneficial bacteria turn the fish waste into fertiliser for the plants, and the cleaned water returns to the fish. The system uses little water and no chemical fertilisers.

The original study describes a 48 m² greenhouse unit on a roof of about 50 m², raising tilapia, basa and eel, and growing strawberries, lettuce, coloured peppers and leafy greens. Tomatoes, aubergines, green peppers and herbs can also be grown.

For a small project, the realistic aim is food for the family plus extra income from selling the surplus. It needs daily care and solid technical knowledge, so it is best to start with a small unit and expand after gaining experience.

• The family itself and neighbours: fish and vegetables are everyday necessities.
• Local fish and vegetable traders, contacted before harvest to offer the available quantities.
• Small restaurants and greengrocers looking for fresh, pesticide-free produce (estimate).
• Health-conscious customers: selling part of the harvest at retail gives higher profit, though it takes more time.

According to the study, the full 48 m² unit holds about 500 tilapia, 50 basa and 150 eels plus 2,000 seedlings, and produces:

• 175 kg of tilapia and 75 kg of basa every 6 months, and 150 kg of eel a year
• 648 heads of lettuce, 405 kg of strawberries and 256 kg of coloured peppers every 6 months

These figures are optimistic, and a beginner will likely produce much less in the first year (estimate). A small unit of 2 to 4 tanks can be expected to give about 80 to 150 kg of fish a year plus a moderate amount of leafy greens (estimate).

Skills needed: water-quality management (pH, ammonia, nitrite, oxygen) (estimate), fish feeding, seedling care and pest control without chemicals. Previous farming or fish-keeping experience, or practical training from a specialist, is strongly advised.

Consult an engineer before building on a roof. Check local municipality, agriculture or fisheries office requirements, and confirm that the chosen fish species may be kept in your country.

• Space: a 48 m² greenhouse in the study; 15 to 25 m² for a small start (estimate).
• Roof strength: an engineer must confirm that the building and roof can carry the tanks, water and fish; one cubic metre of water weighs about one tonne.
• Waterproofing: the roof must be fully tiled or sealed so water does not seep into the concrete and weaken it.
• Shelter: it can run in the open sun, but a greenhouse or shade net is better for temperature control and insect protection.
• Electricity: needed around the clock for water and air pumps; a few hours without aeration can kill the fish, so a battery or solar backup is essential (estimate).
• Water: only to top up evaporation.

• Power cuts and fish deaths: battery or solar backup for air pumps, and no overstocking.
• Weak roof or leaks into concrete: prior engineering check, full waterproofing and spread loads.
• Poor water quality and fish disease: regular testing, moderate feeding and full system cycling before stocking.
• Extreme heat or cold: greenhouse with summer shading and winter cover, and species suited to the climate.
• Insects and plant pests: nets and natural control only, because pesticides harm the fish.
• Over-optimistic profits: a reader commenting on the original study argued that such units barely cover costs and suit household use best; start small and track real costs.
• Species restrictions: some countries restrict non-native fish; use only permitted species.

Aquaponics combines fish farming with soil-free plant growing. Fish live in tanks, and their nutrient-rich water is pumped to beds and pipes planted with vegetables. Beneficial bacteria turn the fish waste into fertiliser for the plants, and the cleaned water returns to the fish. The system uses little water and no chemical fertilisers.

The original study describes a 48 m² greenhouse unit on a roof of about 50 m², raising tilapia, basa and eel, and growing strawberries, lettuce, coloured peppers and leafy greens. Tomatoes, aubergines, green peppers and herbs can also be grown.

For a small project, the realistic aim is food for the family plus extra income from selling the surplus. It needs daily care and solid technical knowledge, so it is best to start with a small unit and expand after gaining experience.

• The family itself and neighbours: fish and vegetables are everyday necessities.
• Local fish and vegetable traders, contacted before harvest to offer the available quantities.
• Small restaurants and greengrocers looking for fresh, pesticide-free produce (estimate).
• Health-conscious customers: selling part of the harvest at retail gives higher profit, though it takes more time.

According to the study, the full 48 m² unit holds about 500 tilapia, 50 basa and 150 eels plus 2,000 seedlings, and produces:

• 175 kg of tilapia and 75 kg of basa every 6 months, and 150 kg of eel a year
• 648 heads of lettuce, 405 kg of strawberries and 256 kg of coloured peppers every 6 months

These figures are optimistic, and a beginner will likely produce much less in the first year (estimate). A small unit of 2 to 4 tanks can be expected to give about 80 to 150 kg of fish a year plus a moderate amount of leafy greens (estimate).

Skills needed: water-quality management (pH, ammonia, nitrite, oxygen) (estimate), fish feeding, seedling care and pest control without chemicals. Previous farming or fish-keeping experience, or practical training from a specialist, is strongly advised.

Consult an engineer before building on a roof. Check local municipality, agriculture or fisheries office requirements, and confirm that the chosen fish species may be kept in your country.

• Space: a 48 m² greenhouse in the study; 15 to 25 m² for a small start (estimate).
• Roof strength: an engineer must confirm that the building and roof can carry the tanks, water and fish; one cubic metre of water weighs about one tonne.
• Waterproofing: the roof must be fully tiled or sealed so water does not seep into the concrete and weaken it.
• Shelter: it can run in the open sun, but a greenhouse or shade net is better for temperature control and insect protection.
• Electricity: needed around the clock for water and air pumps; a few hours without aeration can kill the fish, so a battery or solar backup is essential (estimate).
• Water: only to top up evaporation.

• Power cuts and fish deaths: battery or solar backup for air pumps, and no overstocking.
• Weak roof or leaks into concrete: prior engineering check, full waterproofing and spread loads.
• Poor water quality and fish disease: regular testing, moderate feeding and full system cycling before stocking.
• Extreme heat or cold: greenhouse with summer shading and winter cover, and species suited to the climate.
• Insects and plant pests: nets and natural control only, because pesticides harm the fish.
• Over-optimistic profits: a reader commenting on the original study argued that such units barely cover costs and suit household use best; start small and track real costs.
• Species restrictions: some countries restrict non-native fish; use only permitted species.