Pond Supplies & Equipment

For goldfish, aim for at least 500 gallons; for koi, plan on 1,000 gallons or more so they have room to grow and the water stays stable. Bigger ponds are actually easier to keep because temperature and water chemistry change more slowly. Aim for at least 2 feet of depth to keep water cooler in summer and protect fish in winter.

Yes — any pond with fish needs a pump to circulate water and a filter to process waste, just like an aquarium. As a rule of thumb the pump should turn over the pond’s entire volume about once per hour. Skipping filtration leads to murky, unhealthy water and stressed fish.

Clear water comes from balance: adequate filtration, not overstocking or overfeeding, and adding aquatic plants that compete with algae for nutrients. A UV clarifier eliminates the suspended algae that causes green water. Regular partial water changes and removing debris also make a big difference.

Hardy fish like koi and goldfish can overwinter outdoors if the pond is deep enough (at least 2 to 3 feet) so it does not freeze solid. Keep a small area of the surface ice-free with a de-icer or aerator so gases can escape. Fish become dormant in the cold and should not be fed once temperatures drop.

Koi and goldfish — including comets and shubunkins — are the classic, hardy choices. Goldfish stay smaller and suit modest ponds, while koi grow large and need more volume and stronger filtration. Add fish gradually so your filter can keep pace with the bioload.

A koi pond should be at least 3 feet deep, and 4 feet or more is better in very hot or cold climates. The extra depth gives koi room, keeps the water temperature stable, and offers protection from predators and hard winter freezes.

No — once the water drops below about 50°F (10°C), pond fish slow down and their digestion nearly stops, so feeding can actually harm them. Stop feeding for winter and resume in spring once the water warms consistently. Use a wheat-germ food during cool transition periods.

Reduce excess nutrients by not overfeeding or overstocking, add plenty of aquatic plants, and provide shade with floating plants like water lilies. A UV clarifier handles green water, while barley straw and regular debris removal help with string algae. Remember some algae is normal and even healthy.

A UV clarifier passes pond water past an ultraviolet bulb that kills the free-floating algae causing green water, then your filter removes the clumped particles. If you battle persistent green water, it is one of the most effective fixes available. It does not harm fish, plants, or the beneficial bacteria in your filter.

Yes — aquatic plants are one of the best tools for a healthy pond. They absorb the excess nutrients that would otherwise feed algae, oxygenate the water, and give fish shade and shelter. A mix of marginal plants, submerged oxygenators, and floating plants like water lilies works well.