Aquarium keeping in the UK

Units: litres and imperial gallons

In the UK, tanks are usually sold in litres; older hobbyists and some products still refer to imperial gallons (1 imp gal about 4.55 L, so larger than a US gallon). When following stocking or heater guides that use gallons, convert: 1 US gallon about 3.78 L, 1 imperial gallon about 4.55 L. Dosing bottles (e.g. dechlorinator) may be in ml per litre; check the label.

Hard water is the norm

Much of the UK, especially the South and East, has hard, alkaline tap water (high GH/KH). That suits livebearers like guppies, platies, and mollies, and many cichlids. Soft-water species (e.g. some tetras, discus) may need RO or softened water. Test your tap and use a dechlorinator for every water change.

Retail and clubs

Pets at Home and Maidenhead Aquatics (often in garden centres) are widespread; independents and specialist aquatics shops offer more variety and expertise. The OATA (Ornamental Aquatic Trade Association) represents the trade. Local fishkeeping clubs and forums are great for advice and rehoming. Track your tanks in App-aquatic wherever you buy.

Regulations (DEFRA and invasive species)

DEFRA and devolved administrations regulate invasive non-native species. It is illegal to release aquarium fish or plants into the wild. Some species are banned or restricted. After Brexit, imports of live fish and plants from the EU are subject to border and biosecurity rules. Buy from reputable dealers who comply with the law.

Quick takeaways

• UK tanks are in litres; convert from US or imperial gallons when using US-based guides.
• Hard water is common; choose fish that thrive in it or plan for RO or softening.
• Pets at Home, Maidenhead Aquatics, and independents; clubs and forums are valuable.
• Never release fish or plants; follow DEFRA and invasive species regulations.