Herons, cats and protecting a fish pond

If you keep fish, sooner or later something will try to eat them. In much of the UK that means a grey heron standing at the edge early in the morning, and sometimes a cat crouched on the coping. A wildlife pond with no fish has much less to attract them. A goldfish or koi pond is a feeding station.

Nothing on this page makes a pond safe for children. A heron net, a cat deterrent and a child-safety grille are three different things. If young children live in the house or visit, read pond safety for children first. It covers the RoSPA options: a rigid grille strong enough for a child, a proper fence, or filling the pond in for now.

How herons hunt a garden pond

A heron usually lands near the pond and walks in, rather than diving. It stands in the shallows or at the edge and waits for fish to come within reach. That is why the shape of the pond, and what is at its edge, matters as much as anything you put over it.

Shallow margins and a gently sloping edge are good for wildlife and convenient for a heron. That does not mean you should remove them from a wildlife pond. It does mean a fish pond needs some deeper water and some cover where the fish can get away.

Cover nets

A net stretched over the whole pond is the most direct barrier. A pond cover net is sold for leaves and predators, pegged out past the edge so a heron cannot reach the water through it.

What makes a net work:

• It is taut and pegged beyond the edge. A slack net lets a heron push down into the water, and a heron can walk round a net that stops at the waterline.
• It sits above the water. A net lying in the water is easy to reach through and gets tangled in plants.
• It is checked. Wildlife, including hedgehogs and birds, can tangle in loose netting. Look at it regularly and keep it tight.
• It is made for ponds. Use a net sold as a pond cover net. Plant-protector netting and galvanised wire netting are made for other jobs, and this site does not recommend them as pond nets.

A net has a cost for the pond. It blocks some light, keeps out insects that would land on the water, and gets in the way of plants and maintenance. Many people use a net during the season when herons are most persistent, or permanently over a small, formal fish pond, and leave a wildlife pond open.

Pond winter care covers using a cover net for leaves in autumn, and the product example on that page.

A net is not a child cover

A pond cover net keeps out leaves and birds. It is not designed to take a child's weight, and a child can get under it or tangle in it. The child safety page says the same about leaf nets and about the light plastic grids sold as heron or cat deterrents. Do not let a net, a floating grid or a line of wire change your decision about children. Follow the RoSPA advice on that page.

Monofilament lines and edge barriers

Some pond keepers run a low line, or two, around the edge of the pond on short posts, so a heron walking in meets something it cannot see clearly. Others use a low fence or a raised edge on the side where a heron lands.

These are deterrents, not guarantees. Herons learn, and a gap anywhere is a gap. Lines and low fences can also trip people and trap wildlife, and a line at ankle height across a garden path is a hazard. If you use them, keep them where people do not walk and check them often.

Decoy herons are sold on the idea that a heron will not land near another. Opinions differ on whether they work for long. This page does not make a claim either way.

Planting and depth for cover

Fish that can hide are harder to catch. Ways people give them cover:

• Deeper water. Part of the pond deeper than a heron can comfortably wade. How big should a garden pond be has the RHS depth figures.
• Floating leaves. Waterlilies and other floating plants give fish shade and somewhere to hide from above.
• Shelters. Pond shops sell fish caves and shelters, and some people use sections of pipe on the bottom.
• Steeper sides where the heron would stand. On a fish pond, a steeper edge on one or two sides gives a heron less shallow water to stand in. Keep at least one escape route for wildlife elsewhere.

Cats

Cats usually fish from the edge rather than wading in. A coping that overhangs the water, or a flat stone at the edge, gives them a perch. A net stops them reaching the water, and so does planting at the edge that leaves no comfortable place to crouch.

Wildlife ponds

If the pond is for wildlife, as in how to build a wildlife pond, a heron visiting is part of the wildlife. It may take some frogs or newts. That is how a natural pond works. The bigger risk to a wildlife pond is a net or a line that tangles the hedgehogs and birds you were trying to attract.

What not to do

Herons are wild birds and are protected by law. Do not try to harm or trap them. Stick to barriers, cover and deterrents. If you are unsure what is allowed, look at the official wildlife guidance on GOV.UK or contact a wildlife charity rather than relying on a forum.

Will a pond net stop herons?

A taut net, pegged beyond the edge and sitting above the water, is the most direct barrier. A slack net, or one that stops at the waterline, is much less effective.

Can I use a heron net as a child-safety cover?

No. A heron net is not designed to take a child's weight, and a child can get under it. Follow the RoSPA advice on the child safety page: a rigid grille strong enough for a child, a proper fence, or fill the pond in.

Do decoy herons work?

Views differ, and this page makes no claim. A net, deeper water and fish cover are the measures that act directly.