Galvanized canvas fish pond water-system design

Zero-discharge land-based circulating system: a 400 m³ canvas pool body suits a purification pond of about 5 mu at 2 m depth — too large wastes breeding area, too small cleans poorly (small ponds should be 3–4 m deep). Selecting the pond: 3–5 m diameter for fry; 6–10 m for grow-out fish (over 10 m, sewage discharge weakens; fine for storage). Galvanized canvas ponds are economical and last about 8 years; iron-frame canvas ponds are easier to install/disassemble and suit short leases. Sewage design: use a pot-shaped cone bottom at about 10:1 radius-to-depth ratio — a 6 m pond with a 30 cm cone, a 10 m pond with a 50 cm cone. A 6 m pond uses a 110 mm discharge pipe; a 10 m pond uses 160 mm. A middle sleeve or drilled boundary pipe works well; a U-shaped pipe controls the water level, discharging directly or through a central line to the purification pond. Equipment matching: a 3.0 kW submersible supply pump (with standby), 160 mm supply line and a 75 mm switchable inlet; two Roots blowers (2.2 kW and 3.0 kW) as independent aeration systems that can run separately or together, with a 2.2 kW motor as standby.