Fish are a natural part of the wildlife of bigger ponds.
Many animals, such as common toads, some dragonflies and some of the many species of lesser water boatmen live perfectly happily with fish. Lots of water plants don't mind fish either. And of course our native fish are wildlife themselves!
But fish can also damage ponds by
- stirring up silt, which cuts out light needed by water plants
- excreting nutrients into the water (encouraging soupy green 'blooms' of algae)
- uprooting and eating submerged water plants
- eating smaller animals.
Newt larvae, and especially Great Crested Newts, are particularly sensitive to fish predation, so if your pond has a population of breeding Great Crested Newts avoid introducing fish into it.
Too many fish in small pond
Many smaller ponds naturally wouldn't have fish and these are the ponds used by plants and animals that simply don't get on with fish. So if you've got a small garden pond its often best to keep the fish out if you want to see lots of wildlife.
Problems start when people add more fish to a pond than it would have naturally. Particularly in small garden ponds, half a dozen goldfish can have a very big impact, reducing the pond to a green soup of algae.
Native fish
Ponds with natural fish populations can be fantastic, and of course ponds are important for species like the common eel (now very much less common than it once was) and the crucian carp.
Our native fish, especially crucian carp, can be threatened when other fish species are released into the wild. These problems are worse when ponds are heavily stocked with non-native fish.
Think very carefully before you release fish into any pond
It is illegal to release any fish into ponds or other waterbodies (excluding garden ponds), unless you have consent from the Environment Agency or Scottish Environment Protection Agency, or the pond is in a garden with no connection to other waterbodies such that the fish are not going to be able to escape.
Releasing fish into a pond used by Great Crested Newts may contravene UK and EU Law.
Managing Fish
For more information on controlling fish, especially in ponds associated with Great Crested Newts, you can download the Amphibian and Reptile Conservation advice sheet, 'Fish Control Methods for Great Crested Newt Conservation'.
Angling and ponds
Well-managed fishing ponds can be excellent for wildlife, and provide an important refuge for many freshwater species.
Angling can cause problems when excess amounts of protein-rich baits remain uneaten, adding unwanted nutrients to the pond. This can then lead to algal blooms or excessive duckweed, which then make the pond less good for fish welfare.
Care should also be exercised when removing weed, to create swims for the fish, as over zealous weed removal can result in the pond flipping into an algal bloom type state. Other isses can include litter, discarded line, hooks and transfer of fish diseases through poor sanitation (of nets and boots etc).
