Fish Species Guide UK: Tropical, Coldwater & Marine (2026)
Choose the right fish for your aquarium. Care guides, compatibility charts, and tank size requirements for popular UK species.
Quick Answer: The best beginner fish in the UK are hardy species that tolerate a range of water conditions: tropical options include Neon Tetras, Corydoras, Platies, and Guppies. For coldwater tanks, Goldfish (in appropriate tanks, not bowls) and White Cloud Mountain Minnows are ideal. Always research maximum adult size, tank mates, and minimum tank size before buying any fish.
At a Glance
- Best beginner tropical: Neon Tetras, Corydoras, Platies, Cherry Barbs
- Best beginner coldwater: Fancy Goldfish (min 60L per fish), White Cloud Minnows
- Best community fish: Tetras, Rasboras, Corydoras, Guppies, Platies
- Avoid as beginner: Oscars, Arowana, Discus, Marine fish
- General rule: 1cm of adult fish length per 1 litre of water (approximate)
- Always check: Adult size, temperament, water parameter needs, tank mates
Popular Tropical Fish UK
| Species | Adult Size | Min Tank | Temperament | Difficulty | Link |
|---|---|---|---|---|---|
| Neon Tetra | 3cm | 60L (school of 6+) | Peaceful, shoaling | Easy | Food |
| Corydoras | 5-7cm | 60L (group of 6+) | Peaceful, bottom-dweller | Easy | Food |
| Guppy | 3-5cm | 40L | Peaceful, active | Easy | Food |
| Betta (Siamese Fighter) | 6cm | 20L (solo male) | Aggressive to males | Easy-Medium | Food |
| Platy | 5cm | 60L | Peaceful, livebearing | Easy | Food |
| Cherry Barb | 5cm | 60L (school of 6+) | Peaceful, colourful | Easy | Food |
| Bristlenose Pleco | 12-15cm | 100L | Peaceful, algae eater | Easy | Food |
| Angelfish | 15cm | 150L (tall tank) | Semi-aggressive, cichlid | Medium | Food |
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Popular Coldwater Fish UK
| Species | Adult Size | Min Tank | Temperament | Notes |
|---|---|---|---|---|
| Fancy Goldfish | 15-20cm | 60L per fish | Peaceful | Do NOT keep in bowls. Need filtration and space |
| Common Goldfish | 25-35cm | Pond only | Peaceful | Too large for most indoor tanks. Pond fish |
| White Cloud Minnow | 3-4cm | 40L (school of 6+) | Peaceful, shoaling | Excellent beginner coldwater fish |
| Weather Loach | 20-25cm | 120L | Peaceful, bottom | Active, entertaining. Needs sand substrate |
Tank Mate Compatibility
Common Mistakes to Avoid:
- Goldfish with tropical fish — Different temperature needs
- Male Bettas together — Will fight to death
- Large cichlids with small tetras — Tetras become food
- Common Plecos in small tanks — Grow to 30-45cm, need 200L+
- Tiger Barbs with long-finned fish — Barbs nip fins aggressively
- Goldfish in bowls — Bowls are too small, unfiltered, and inhumane
Frequently Asked Questions
What is the easiest fish to keep?
Guppies, Platies, and White Cloud Mountain Minnows are among the easiest. They tolerate a range of water conditions, eat standard flake food, and breed readily. For a single-species setup, a Betta in a 20L+ heated, filtered tank is also very manageable.
How many fish can I keep in my tank?
The rough guide is 1cm of adult fish length per litre of water, but this varies significantly by species. Active swimmers need more space than sedentary fish. Bottom-dwellers use different space than mid-water fish. Always research specific species requirements and err on the side of fewer fish — understocked tanks are healthier and easier to maintain.
Can I keep a goldfish in a bowl?
No. Goldfish bowls are too small, lack filtration, and cannot maintain stable water quality. Fancy goldfish need a minimum of 60 litres per fish with proper filtration. Common goldfish grow to 25-35cm and need a pond or very large tank (200L+). Keeping goldfish in bowls causes suffering and dramatically shortens their lifespan (from 10-15+ years to months).
Key Terms
Sources
- Practical Fishkeeping — Species Profiles
- OATA — Ornamental Fish Care Guides
- RSPCA — Fishkeeping Standards
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