Non-native fish, crustacea, snails, clams and mussels that can live in garden ponds or temperate (unheated) aquariums may be able to survive in our climate so could harm native species if they are released or escape into the wild. It may also be an offence to release a non-native animal, or allow it to escape, into the wild. 

Owners should follow the main Don't let them loose guidance, and additional guidance below under Recommendations to help prevent this from happening.

Some species of non-native fish and crayfish are controlled, and a licence is required to keep them (including their live eggs).

You should check whether the species you keep, or intend to keep, are controlled at:

• England and Wales: Introduce or keep non-native fish and shellfish - GOV.UK
• Scotland: Freshwater fisheries licensing - gov.scot

The following fish and crayfish are included on the list of species of special concern:

• Lepomis gibbosus, Pumpkinseed
• Orconectes limosus (Faxonius limosus), Spiny-cheek crayfish
• Orconectes virilis (Faxonius virilis), Virile crayfish
• Pacifastacus leniusculus, Signal crayfish
• Percottus glenii, Chinese sleeper/Amur sleeper
• Plotosus lineatus, Striped eel catfish
• Procambarus clarkii, Red swamp crayfish
• Procambarus fallax f. virginalis (Procambarus virginalis), Marbled crayfish
• Pseudorasbora parva, Topmouth gudgeon (also known as stone moroko)

If you own one of the species above there are other considerations that you must also check here:

• England and Wales: Invasive non-native (alien) animal species: rules in England and Wales - GOV.UK
• Scotland: Legislation and responsibilities.

Recommendations

All cold water fish and aquatic invertebrates – read this first

• Take care when sourcing plants for your pond or aquarium – check they are not harbouring unexpected ‘hitchhikers’ that could cause problems. These could be tiny plant fragments, eggs, or small organisms like snails. If you find something, see what to do if you find a 'hitchhiker' for advice.
• Dispose of unwanted aquatic plants responsibly, for example by adding them to your garden compost or using them as mulch (away from waterbodies or drains) – do not wash them down drains or place them in rivers or other waterbodies as they could become invasive. Check out the Be Plant Wise campaign for more information.
• To prevent unwanted young, monitor your pond or aquarium for eggs that could be removed and destroyed.
• If you find unwanted young, or no longer wish to keep your pond or aquarium, you will need to rehome any fish or invertebrates. See what to do if you can no longer keep your pet for advice. Do not release any animals from your pond into any other waterbodies, except if you are moving them from one garden pond into another.
• Most freshwater fish species must only be kept in indoor aquaria and not in any outdoor ponds or water features, even if just for summer periods, see Introduce or keep non-native fish and shellfish - GOV.UK.

Garden ponds

• When creating a pond, design it to ensure it is not connected to any natural watercourses and is not on land that is at risk of flooding – you can use the following resources to check the flood risk near you:
  • England: Check the long term flood risk for an area in England - GOV.UK
  • Scotland: Flood maps | Scottish Environment Protection Agency
  • Wales: Check your flood risk on a map (Flood Risk Assessment Wales Map)
• If you have a pond that is connected to a watercourse, you must control the outflow to prevent any non-native plants, fish, snails or other animals from escaping, for example by installing a fine mesh or screen over the outflow pipe.
• Have a plan for what you would do to temporarily move your fish and invertebrates to a safer place if there is a flooding risk.

Temperate (unheated) aquariums

• Treat used substrate or décor before disposal to ensure that it does not contain escaped animals, live-foods, or pathogens. This can be done by freezing waste material for 48 hours or baking it in an oven.
• Check any aquatic plants you remove for ‘hitchhikers’, such as crustacea, molluscs or cleaner species, and return these to your aquarium.
• Empty used aquarium water onto your lawn or flowerbed, or into the sink or toilet if you don’t have access to a garden. Do not empty it into or near outdoor drains, ponds or watercourses as there may be all sorts of hidden life, like tiny invertebrates or cleaner species, that could escape into native waterways and become invasive.
• A care sheet with more information on disposing of ‘hitchhikers’ and decontaminating your aquarium is available from OATA.