Interactive lesson

Building a fish pond, step by step

Interactive lesson: a fish pond you can drain and harvest — bottom profile, digging, monk, inlet with a screen, heron protection and first filling.

Free sample Chapters 1 and 2 (8 steps) are free. The full lesson comes with the Building a small fish pond module. Already bought? Unlock

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The whole lesson as text

1. A fish pond is not just a pond

A fish pond is a pond you can fill, and drain to the last drop, whenever you need to.

Outlet to the bottom — A fish pond must have an outlet down to the bottom: a monk or a pipe with an elbow. Through it you drain the water in autumn and hold the level in summer.
A falling bottom — Within each zone the bottom falls 0.2–0.5 % towards the outlet, which is 20–50 cm per 100 m. A flat bottom leaves puddles all over it.
Catch pit — In front of the outlet: 2–4 m² and 30–50 cm deeper than the bottom, lined with gravel or concrete slabs. In the end all the fish gather here.
Screen and grille — The inlet runs through a screen, the spillway and outlet through a grille: your fish don't get out, wild fish don't get in.

Why: No outlet means no harvest, no cleaning and no rescue when something goes wrong. Skip it and in autumn you wade through mud up to your waist, and half the fish stay in the silt.

If you already have a pond, don't add fish to it. Better to build a new pond next to it and keep the old one as a wildlife pond for frogs and dragonflies.
This module follows on from H04-05 Ponds and keeping water in the soil: that is where the water-holding test, clay, liners and safe banks are.

2. Size and shape

Shape and depths decide whether you can harvest the pond.

150 to 1,000 m² — Under 150 m² a pond gets too warm in summer and quickly runs out of oxygen. Over 1,000 m² (about a quarter of an acre) it is hard to harvest without help and a seine net.
A rectangle — The long side 2–3 times the short side, with the outlet on the short, lower side. Easy to harvest, line and calculate.
Shallow and deep — Shallow end at the inlet: 0.6–1 m of water, where the water warms and food grows. Deep end at the outlet: 1.5–2 m (5–6½ ft), where fish overwinter under ice.
Banks — At least one safety bank with a 1 : 3 slope and a shallow shelf of 20–30 cm, so people and animals can get out. The others 1 : 2, straight down to 60–80 cm depth.

Why: A pond shallower than 1 m over its whole area heats above 28 °C (82 °F) in summer and in a hard winter freezes almost to the bottom. Deeper than 2.5 m makes no sense on a small homestead: the bottom water is cold and without oxygen.

Don't make bays and peninsulas: fish hide in them at harvest.
A steep bank protects fish from herons, but a child who falls in can't climb out. Fence the pond while children are small.