Which Fish Is Good for Water Lily Pond?
Photo by charlieishere (CC BY 2.0)
Goldfish are the best choice for water lily ponds because they eat mosquito larvae while leaving your plants alone, whereas Koi-though popular-become destructive diggers and plant-eaters as they mature beyond a few inches. Understanding which fish work and which don't is essential if you want thriving water lilies alongside a healthy pond ecosystem.
Why You Need Fish in a Water Lily Pond
Water lilies attract more than just admirers-they attract mosquitoes. If left unchecked, mosquitoes will breed in your pond and emerge as biting adults. The simplest and most natural control is to stock a few fish.
What fish do for mosquito control:
- Eat mosquito larvae before they mature
- Snap up adult mosquitoes laying eggs on the water surface
- Require no chemicals or manual intervention
While you can use mosquito dunks (a biological control available at most garden stores) as an alternative, live fish solve the problem passively while adding movement and visual interest to your pond. However, not all fish are created equal when water lilies are the priority.
Why Goldfish Are Ideal for Water Lily Ponds
Goldfish are the standard for water lily ponds, and for good reason. They are colorful, hardy, and-most importantly-safe around your lilies.
Goldfish benefits:
- Do not eat or damage water lily pads or foliage
- Control mosquito larvae effectively
- Tolerate the cool, oxygenated conditions of outdoor ponds
- Hardy in freezing climates (with adequate pond depth)
- Relatively low-maintenance
A healthy population of goldfish will keep your water lilies visible in clear water while preventing mosquito infestations. They thrive in water lily ponds and rarely cause the problems that plague other species.
Koi: Why They Don't Work with Water Lilies (Usually)
Koi are beautiful, impressive fish that appeal to many pond keepers-but they're a poor match for water lilies, especially as they grow.
The problems with Koi in lily ponds:
1. Size and appetite
Koi grow to 2-3 feet long and develop a taste for plants. Young Koi seem well-behaved, but once they exceed a few inches, they begin consuming bog plants and water lily foliage.
2. Rooting and uprooting
The most destructive Koi behavior is their instinct to dig in the substrate. They root around looking for food, uproot planting containers, and scatter mud across the pond bottom. This turns clear water murky and destabilizes your lily plantings.
3. Gravel destruction
Koi love to pick up pea gravel in their mouths and spit it out, gradually exposing bare soil where they can dig deeper into plant containers.
If you must keep Koi with water lilies:
The one successful workaround is to replace standard pea gravel with lava rock gravel. Lava rock is rough and sharp, so Koi dislike picking it up and are less likely to dig. This reduces (but doesn't eliminate) damage. However, even this solution isn't foolproof-smaller Koi may still uproot containers and eat tender plants.
Most experienced pond keepers who've tried Koi with lilies eventually remove the fish. As one respected water garden hobbyist put it after seeing a neighbor's Koi-damaged pond: "I would never put Koi in my ponds since they were too destructive to my water lilies." That's advice worth heeding.
Other Fish to Avoid or Approach with Caution
Beyond Koi, several other fish pose problems for water lilies:
Herbivorous and bottom-feeding fish (like plecos or certain catfish species) may nibble or damage plants. Redtail catfish, for example, are far too large and destructive for most lily ponds.
Ducks aren't fish, but they're worth mentioning: they actively eat water lily pads and are incompatible with a planted pond.
Fish that require warm water (most tropical species) aren't practical in outdoor ponds in temperate climates, and adding heaters defeats the purpose of a low-maintenance pond.
Setting Up a Successful Fish-and-Lily Pond
Once you've decided on goldfish, a few simple practices keep everything balanced:
1. Stock appropriately
Don't overstock. A small garden pond (under 100 gallons) needs only 2-4 goldfish. In stock tanks or larger ponds, allow roughly 1 goldfish per 10-15 gallons.
2. Protect planting containers
- Use 8-quart dish pans or shallow, sturdy containers (avoid lightweight flower pots that fish can overturn)
- Top each container with 1 inch of pea gravel to anchor soil
- Plant one lily per container-they grow large and need room
3. Position lilies away from water disturbance
Water lilies thrive in still, calm water. If you have a waterfall or fountain, move lily containers away from splashing water. In nature, lilies grow in ponds and lakes, never in moving water like rivers.
4. Maintain adequate depth
- Ideal depth for lilies is 2 feet
- For goldfish in cold climates, 18-24 inches keeps them safe when ice forms
- Koi require even deeper water (3+ feet), another reason they're less suited to small lily ponds
5. Don't overfertilize
Fertilizing water lilies also feeds algae. Use lily-specific fertilizer tablets monthly during the growing season, but stop in early fall. If your pond stays small and manageable, you may skip fertilization entirely-lilies will bloom less prolifically but still thrive.
Common Lily Pond Fish Myths
"I need a large filter system if I have fish and lilies."
Not necessarily. Goldfish in a well-planted lily pond with adequate surface area often achieve balance without mechanical filtration. Lilies themselves help reduce algae by blocking sunlight. Monitor water clarity; if it becomes persistently murky, add a biological filter or increase water changes.
"Any small fish will work."
Not true. Small fish like mosquitofish are effective for mosquito control but can't be seen or appreciated. If you want ornamental value alongside mosquito control, goldfish are the standard for good reason.
"Koi are just large goldfish."
While both are carp relatives, Koi have very different feeding behaviors and destructive habits. Don't assume they'll behave like goldfish at larger sizes.
Introducing Fish to Your Pond Safely
If you're starting fresh or adding fish to an established pond, acclimate them gradually. Float the fish in a bag on the water surface for 15-20 minutes so temperatures equalize, then gently release them. This prevents shock and injury.
Wait at least 2-3 weeks after establishing lilies before adding fish, allowing roots to anchor firmly in their containers.
When Not to Keep Fish
You don't actually need fish in a lily pond. If you prefer a plant-only aesthetic or are concerned about predators, use mosquito dunks-small donut-shaped pellets of biological control (containing Bacillus thuringiensis subspecies israelensis) available at garden centers. One dunk lasts about a month and works well in bog gardens and small containers where fish aren't practical.
Fish are optional; lilies are the star. Choose fish only if you want them.
Frequently asked questions
Can I keep both goldfish and Koi together in a water lily pond?+
Yes, physically possible, but not recommended. Young Koi may coexist peacefully with goldfish initially, but as Koi grow (reaching 2-3 feet), they become aggressive diggers and plant-eaters. Goldfish are peaceful and won't interfere with Koi, but Koi will uproot lily containers and damage plants that goldfish rely on for cover and habitat. It's better to choose one or the other based on your primary goal.
How many goldfish do I need to control mosquitoes in my pond?+
For a small garden pond (50-100 gallons), 2-4 goldfish are sufficient to manage mosquito larvae. In larger ponds, plan for roughly 1 goldfish per 10-15 gallons of water. The exact number depends on mosquito pressure and water temperature; cooler water means slower fish metabolism and reduced larva consumption, so you may need a few more in northern climates.
Will goldfish eat my water lily flowers or new growth?+
No. Goldfish eat insects, algae, and small invertebrates, but they don't consume water lily pads, stems, or flowers. This is one reason they're ideal for lily ponds. They leave the plants alone while controlling the mosquito larvae that would otherwise infest the water.
What's the best way to prevent Koi from digging up my water lilies?+
The most effective method is to replace pea gravel with **lava rock gravel** over your lily containers. Koi dislike the rough, sharp texture and are less likely to pick it up and spit it out-behavior that typically exposes bare soil for digging. However, lava rock isn't a perfect solution; motivated Koi may still uproot containers. The best approach is simply to avoid Koi if water lilies are your priority.
Can I use mosquito dunks instead of fish to control larvae?+
Yes. Mosquito dunks (containing *Bacillus thuringiensis*) are an effective biological control available at most garden centers. One dunk lasts about a month and works well in both ponds and bog gardens. Dunks are ideal if you prefer a plant-only pond or don't want to maintain fish, though many hobbyists find fish more convenient and visually appealing.
What water temperature do goldfish need in a pond?+
Goldfish are coldwater fish and thrive in outdoor pond temperatures, even in freezing climates, provided the pond is deep enough (at least 18-24 inches) so the crown of the plant doesn't freeze. They actually prefer cooler water and don't need heaters. During winter, goldfish become dormant in cold water and eat very little-this is normal and healthy.