Outdoor ponds are rife with all sorts of animal life. Interaction between amphibians, fish, waterfowl, and reptiles is inevitable in every healthy freshwater system. This establishes a balance, via the natural food chain, and ensures that populations are kept in check. Frogspawn and tadpoles, with hardly any defenses or skills at evading predators, are easy prey and will undoubtedly be consumed in large numbers.
Even captively bred ornamental fish are likely to partake in nature’s bounty, despite the regular provision of fish food with a complete nutritional profile. The peaceful goldfish is no exception. It can consume prey types that its wild counterpart, the common carp, is likely to consume. As goldfish have much smaller mouths and generally don’t grow too large in ponds, however, they’ll stick to fish food and smaller types of prey.
Indeed, tadpoles and frogspawn can be a favorite treat for goldfish. They may even relish in the chase and develop a taste for these critters at the peak of every rainy season. Depending on your goals as a pond keeper, this can be a good or bad thing. The advantages and disadvantages of tadpole consumption to goldfish, their presence in the pond, and ways to avoid or encourage it are discussed below.
Benefits of Having Tadpoles in Your Goldfish Pond
1) A natural food source
In the wild, small fish generally favor tadpoles as they are easy to catch and eat. They are also rich in protein. Natural bodies of freshwater are usually rife with frog eggs and tadpole populations every spring and summer, during which fish are most active and require constant sources of energy.
In ornamental fish ponds, goldfish will occasionally eat tadpoles, especially those that dare to veer close to their mouths. Size is the main factor in tadpole consumption. Large tadpoles are unlikely to become prey to small goldfish, whereas small ones will easily fit into a gaping goldfish mouth. Goldfish are unlikely to make a significant dent in tadpole populations, however, due to the availability of other food sources.
Other freshwater creatures are able to benefit from feeding on frogspawn and tadpoles. These include insect larvae, turtles, and waterfowl. If you’d like to increase biodiversity in a goldfish pond, tadpoles can serve as a lure for these animals.
2) Macro-decomposers
Macro-decomposers are small animals that help break down organic material. Close to the bottom of the food chain, tadpoles can feed on detritus, fish waste, and small pond plants. Their first few weeks of life are spent as specialized herbivores and opportunistic feeders, making them primary consumers and decomposers. Their feeding habits can help hasten decomposition rates, especially if the pond system is able to support a large number of them.
3) Control of algal growth
As obligate herbivores, young frog tadpoles must feed on algae and bacterial biofilm. An abundance of them can exert significant grazing pressure on algal communities, aiding in the prevention of algal blooms. They are self-sufficient feeders that need not venture into the open pond for food.
4) Bioindicators
Frogs don’t usually lay their eggs in polluted or poor-quality water features. They go the extra mile searching for clean water that can bathe their eggs with oxygen and keep their young comfortable. Tadpoles thrive in water conditions that are optimized for ornamental fish. The presence of active tadpoles in a goldfish pond may indicate that nutrient concentrations and oxygen levels are adequate for fish growth and survival.
Dangers of Tadpoles in a Goldfish Pond
1) Some tadpoles are toxic
Unlike frog tadpoles, toad tadpoles can be harmful to goldfish due to their ability to secrete toxins. These are similar to those secreted by the parent toad as a means to ward off potential predators. To begin with, their eggs are quite unpalatable to fish, who will quickly learn to avoid them as a food source. Goldfish may attempt to eat toad tadpoles, but it is likely they will spit them out. The taste is enough to discourage them from making the same mistake!
Common toad tadpoles in ponds include those of the Bufo genus (e.g. Bufo bufo, Bufo marinus), known as common toads. Keep an eye out for adult toads. If they venture in and out of your goldfish pond, you may soon have some potentially toxic tadpoles. Extra measures may be required to prevent your goldfish from accidentally consuming them. These are listed in the next section of this article.
2) Altered pond water quality
A pair of breeding frogs can easily produce a clutch of more than 1,000 eggs. Without the presence of predators, many of these will mature into waste-producing, oxygen-consuming tadpoles. These can significantly raise the pond’s biomass, placing more pressure on its capacity to circulate nutrients. Common symptoms of overpopulation include increased ammonia and nitrogen and decreased dissolved oxygen levels, which can have a lethal effect on goldfish.
If tadpole populations wreak havoc in this way, you can either manually remove them from the pond or encourage your fish to graze on them. If they are toxic toad tadpoles, the former solution is necessary.
3) Altered goldfish feeding habits
If your fish develop a taste for tadpoles, their eagerness to consume artificially produced fish food may be altered. This is rarely observed in goldfish, but may occur if they are deprived of food for some time and grow accustomed to natural food sources.
4) Competition with fry for food
If you’d like your goldfish to breed in ponds, it would be best to remove tadpoles as they can compete with hatchlings for food or consume the fertilized fish eggs before they are even able to hatch. Tadpoles quickly become omnivorous – if they outgrow your fry, they may also end up eating them. They can even cannibalize on one another when food is scarce.
How to Prevent Tadpoles From Occupying the Fish Pond
Some pond owners adopt preventive measures early on to control tadpole populations in their outdoor pond. If you’re worried about the effects tadpoles may have on your system or you’ve noticed that there are toads around your pond, you may consider the options below. A radical means of tadpole culling is the addition of chlorine, but note that this can kill your goldfish too.
- Remove eggs or tadpoles on sight. Use a small fishing net to fish them out and relocate them to a more suitable location.
- Encourage your fish to feed on them by skipping a few feeding sessions. Be cautious when doing so and closely observe your fish for signs of hunger.
- Remove potential forms of shelter for tadpoles. If a large population has become settled in your pond, you may remove some of their hiding places, such as submerged potted plants and marginal features.
- Increase the current in your pond by adding pumps. Frogs prefer to lay their eggs in calm still water to keep the clutch from becoming displaced, so a current may dissuade them from choosing your pond.
- Build a low fence around the pond to keep out amphibians.
How to Promote Tadpole Survival in Your Goldfish Pond
If you’re confident the amphibians in your area are the non-toxic kind, you may want to encourage tadpole growth in your pond due to their many ecosystem services. A naturalized goldfish pond, with features similar to those of a wildlife pond, would surely attract many frogs and increase the survival rates of their spawn.
Complex structural features (e.g. pond plants) along the pond bottom and in the marginal sections of your pond will open up many hiding places for tadpoles, reducing their chances of being eaten by goldfish. Regularized feeding times and fish treats for your goldfish will also discourage them from searching for other food sources.
Tadpoles and goldfish can peacefully prosper in a single pond as long as their basic needs for food, shelter, and good water quality are met. Keep in mind, however, that tadpole presence can be seasonal as they will eventually grow large enough to leave your pond. Those that survive as adult frogs may eventually return to lay their own eggs in the pond the following year.
I created a pond and stream two years ago and was delighted to find tadpoles in the pond each year. I eagerly watched the tadpoles grow, but, just as they were developing discernable legs (not nearly developed or large enough to get out of the water) they disappeared overnight. I could understand it if the fish had eaten them, but why would they wait so many weeks to do this?
Hi Stewart,
I’m sorry to hear about your tadpoles. It’s possible that the fish were waiting for the tadpoles to grow bigger and more nutritious before eating them. Alternatively, there could be other predators in your pond or nearby, such as birds, frogs, snakes, or raccoons, that prey on tadpoles at different stages of their development. You could try to provide some hiding places for the tadpoles, such as rocks, plants, or logs, or cover part of the pond with a net to deter predators. I hope you can enjoy your pond and stream and see some frogs emerge next year.