Choosing Pond Fish: Koi, Goldfish & More
Creating a thriving garden pond starts with choosing the right fish. Whether you dream of vibrant koi gliding through crystal-clear water or a peaceful display of shimmering goldfish, selecting suitable species is key to a healthy, balanced pond.
At Birchwood Aquatic Centre, we’re here to help you find the perfect pond fish for your space, water conditions, and experience level.
Popular Pond Fish Species
Koi Carp
Koi are the kings of garden ponds — stunning, intelligent, and full of personality.
Ideal for: Larger ponds (over 1,000 gallons)
Growth: Up to 2–3 feet
Care: Require strong filtration, good aeration, and regular feeding
Varieties: Kohaku, Sanke, Showa, Butterfly Koi, and more
Koi thrive in stable, well-filtered environments and can live for decades when cared for properly.
Goldfish
A classic choice that’s hardy and colourful. Perfect for smaller or medium ponds.
Ideal for: Beginners and smaller ponds
Growth: 6–10 inches
Care: Low-maintenance and adaptable to UK climates
Varieties: Common, Comet, Shubunkin, Sarasa, and Fantail
Goldfish can live harmoniously in groups and add instant movement and charm to your pond.
Orfe (Golden, Blue & Albino)
Fast-swimming and active, Orfe are perfect for adding liveliness to your pond.
Ideal for: Ponds with good oxygenation and surface movement
Growth: Up to 18 inches
Care: Prefer to be kept in groups of five or more
They’re beautiful, sociable fish that help keep your pond lively and balanced.
Tench (Green or Golden)
Tench are peaceful bottom dwellers that help clean up leftover food.
Ideal for: Natural or wildlife ponds
Growth: Up to 12 inches
Care: Hardy and excellent for mixed ponds
They stir up the sediment gently, helping to keep debris from building up.
Other Pond Fish Options
For something different, consider:
Rudd: A shimmering native species, great for movement at the surface
Sturgeon/Sterlets: Striking but only for large, well-filtered ponds with high oxygen levels
Minnows & Sticklebacks: Ideal for natural or wildlife ponds without large predators
Mixing Species Safely
Not all pond fish are compatible. Larger koi may accidentally swallow small goldfish or minnows, and fish with different temperature or oxygen needs may struggle together.
Before mixing species, check:
Pond size & depth
Filtration capacity
Water temperature & oxygen levels
Feeding requirements
Our team can advise you on the best species combinations for your pond setup.
How Many Fish Can You Keep?
A general guide is 1 inch of fish per 10 gallons of water, but pond shape, filtration, and oxygenation make a big difference.
Tips for Healthy Pond Fish
Perform weekly partial water changes during warm months
Avoid overfeeding – feed only what fish consume in 2–3 minutes
Maintain good aeration and use pond plants to improve oxygen levels
Test water regularly for ammonia, nitrite, and pH
Quarantine new fish before adding to your main pond
Need Expert Advice?
Our staff at Birchwood Aquatic Centre are passionate pond keepers too. We’ll help you choose fish suited to your pond’s size, setup, and maintenance level — ensuring long-term success and a beautiful display all year round.
📍 Visit us in Swanley, Kent, for expert one-to-one advice on pond design, filtration, and fish care.
Frequently Asked Questions
Can koi and goldfish live together?
Yes — koi and goldfish can share a pond as long as it’s large enough, well-filtered, and the koi aren’t big enough to swallow the smaller goldfish. Both species enjoy similar temperatures and feeding habits.
How deep should my pond be for koi?
A: Ideally at least 1 metre (3 feet) deep to protect them from temperature changes and predators. Deeper ponds also help koi overwinter safely.
What fish are best for small ponds?
A: Goldfish, Shubunkins, or small varieties of Sarasa Comets are perfect for smaller ponds. Avoid koi or orfe, as they grow large and need more space.
Can I mix native fish like sticklebacks with ornamental species?
It’s not recommended. Native species may carry parasites or diseases that ornamental fish aren’t used to, and they often have different feeding habits.
How do I keep my pond fish healthy year-round?
Maintain clean, well-oxygenated water, feed appropriately, and test your water regularly. In winter, avoid disturbing the pond’s natural ice layer too much—use a pond heater or air stone instead.
Do I need a filter for goldfish ponds?
Yes — even for goldfish, filtration helps remove waste, maintain clear water, and support beneficial bacteria that keep your pond balanced.
How long do pond fish live?
With good care, goldfish can live 10–20 years, and koi can live 25–50 years or even longer.
Can I add new fish to an established pond anytime?
Only when water quality is stable. Always quarantine new fish for at least two weeks to prevent spreading disease to your existing stock.