37 · Indoor & Aquaponics Ponds
Run a pond indoors and let the fish feed your plants. Aquaponics closes the loop: waste becomes fertilizer.
The loop
Fish waste is converted by bacteria into nitrate, which plants absorb as food. The cleaned water returns to the fish. With balanced stocking, you add only fish food and top-up water.
System types
- Media bed — flood-and-drain gravel beds host bacteria and roots.
- Raft / DWC — plants float on the pond surface in net pots; great for leafy greens.
- NFT — thin film feeds roots; less buffer, needs careful control.
Balance & monitoring
Too many fish fouls the water; too few plants starves the cycle. Aim for light stocking, monitor ammonia/nitrite (should read zero), and keep pH in the 6.5–7.2 band plants and fish both tolerate.
Indoor note
Indoor ponds need a calm surface or lid to manage humidity, plus grow lights for plants through winter. A small aerator keeps oxygen high where plants are not photosynthesising.
Caveats
Power loss is fatal fast indoors — add a battery-backed air pump. Pesticides, cleaning sprays, and cooking fumes near the pond can wipe the system.
Aquaponics setup procedure
- Set up the fish tank (200–500 litres minimum).
- Install a pump to move water to the grow beds.
- Fill grow beds with clay pebbles or perlite (not soil).
- Plumb the return so water drains back to the fish tank by gravity.
- Start the cycle: add ammonia source (fish food or ammonia), wait 4–6 weeks for bacteria to colonise.
- Add fish gradually: 1–2 fish per 50 litres.
- Plant seedlings into the grow beds once ammonia and nitrite read zero.
Best aquaponics crops
- Lettuce, rocket, watercress (fast-growing, low nutrient demand).
- Tomatoes, peppers, cucumbers (higher demand, need more fish).
- Herbs: basil, mint, coriander.
- Avoid root vegetables (potatoes, carrots) — they do not grow well in clay pebbles.