Tadpoles are active critters that are found in just about every naturalized outdoor pond. They are often indicators of favorable water conditions and a well-balanced pond system. When found in reasonable numbers and structurally diverse ponds, they can live in harmony with fish. Their survival is determined by a host of factors, including their size and abundance relative to potential predators.
Depending on a pond owner’s intention for their outdoor pond, tadpoles can be viewed as wholly beneficial or detrimental. In this sense, you may opt to have fish that are either naturally carnivorous or less likely to eat food other than carbohydrate-rich feeds and plant material. Generally, pond fish that require high-protein diets will jump at the chance to gobble up an unsuspecting tadpole. Their tendency to do so will largely be influenced by the regularity of feed provision.
Moreover, tadpole consumption may be reinforced or discouraged through multiple means. If you dislike tadpoles and would like your fish to graze down their populations, it would make sense to eliminate potential hiding places. Conversely, if you favor tadpoles, you can add floating and submerged plants to keep them hidden from hungry fish. That being said, tadpoles that do manage to survive will eventually leave the pond system. Listed below are some common pond fish that perceive them as seasonal treats!
1) Koi (Cyprinus rubrofuscus)
This ornamental pond staple is known as a peaceful and friendly species, but it does have a knack for eating tadpoles. Outdoor koi ponds tend to have conditions that are suitable for tadpole growth, so their marginal plants and floating fronds attract many frogs. If fish feeding sessions are skipped or koi find themselves hungry in between, they may search for natural sources of food. As omnivores, they can feed on both pond plants and smaller fish. Koi consume a large amount of their own larvae, with which they may even confuse tadpoles!
A good way to prevent larger koi from feeding on larvae would be to create a pond shelf or shallow pockets. Plants with either shoots or roots that grow throughout the water column can also serve as a protective barrier. Nonetheless, koi that are trained to feed on the water’s surface will seldom serve as an effective means of tadpole control. They won’t deliberately roam the pond in search of little critters to eat. If tadpole and frog populations do get out of hand, other voracious carnivores may have to be introduced.
2) Goldfish (Carassius auratus)
With over a hundred breeds, goldfish seem to come in all shapes and sizes. Some stay quite small all throughout their lives, with mouths that are able to accommodate only pea-sized objects. Others manage to reach larger sizes, especially if they are reared in low-density, considerably sized ponds. In this case, tadpole consumption is mostly size-dependent. Freshly hatched tadpoles, due to their minute size, are more vulnerable.
As goldfish are smaller than koi, they can easily navigate through shallow areas and gaps in vegetation. Exposed frogspawn will certainly satisfy goldfish that are in search of a protein-rich dinner. Those that are left unscathed and do manage to hatch into tadpoles would be beneficial in a goldfish pond. They may help regulate goldfish populations by directly competing with their offspring for food. Goldfish are known for breeding like rabbits, so a little competition is necessary to maintain a balanced ecosystem.
Like koi, goldfish that are accustomed to a feeding schedule and high-quality feeds are less likely to consume pond critters. On their own, they should not be relied upon as a biocontrol agent for tadpole populations. Keep in mind that removing pond structures that shelter tadpoles, as a means to expose them to predators, may also make your fish more susceptible to predation.
3) Betta (Betta spp.)
Among all the popular types of aquairum fish, those classified under the Betta genus are unarguably some of the smallest and are sometimes also kept in tropical wildlife ponds. In the wild, these fish are often found in slow-moving streams, ponds, rice paddies, ditches, and shallow pools. These same habitats are prime spots for breeding frogs, which is why bettas and tadpoles may directly compete with one another for food.
Despite their tiny jaws and cheeks, bettas are natural carnivores. They target the larval forms of many animals, including amphibians. However, their capacity to consume tadpoles is limited by their size. Freshly hatched tadpoles with a full body length that is just about a fifth or less of a betta are likely to be eaten. Interestingly, betta may attack and disembowel tadpoles before consuming them either whole or in parts. The whole thing is a grisly affair as unsuspecting tadpoles can’t simply disappear into a betta’s tiny mouth.
Just as bettas may eat the smallest of tadpoles, they may also be fair game to larger fish. Fortunately for them, their small size allows them to hide in nooks and crannies in the pond, just as tadpoles do. The shared microhabitat is perhaps what compels them to go after tadpoles in the first place. This rings true especially because bettas are quite dominant and are known for being formidable fighters. They also have a reputation for being extremely hardy and surviving just about anywhere.
4) Western & Eastern mosquitofish (Gambusia affinis, Gambusia halbrooki)
Contrary to the implications of its common name, the mosquitofish diet is mostly composed of mayflies, beetles, zooplankton, and mites. Mosquito larvae are certainly eaten, but are seldom the primary food choice. It turns out that mosquitofish can be quite a threat to amphibian survival as well. They are capable of devouring large amounts of tadpoles.
One study that explored their capacity for newt tadpole consumption found that they could eat a significant portion of tadpoles when present in both high and low densities. Who would’ve thought that these tiny fish, growing to a maximum length of just 4 cm (1.6 inches) could make such a dent in frog hatchling numbers? Of course, it goes without saying that they would only be effective when introduced at the right time. The tadpoles have to be small enough to fit into the mosquitofish’s mouths.
5) Pumpkinseed sunfish (Lepomis gibbosus)
Though they weigh less than a pound at maturity, pumpkinseed sunfish can grow to a maximum length of 11 inches (28 cm). This slim-bodied species is also known as pond perch, kivver, punky, and sunny. Due to its vibrant coloration, it has become popularized as an ornamental fish and introduced into many areas outside of its native range. Unfortunately, this fish is quite the competitor and is now considered invasive throughout most of Europe.
Pumpkinseed sunfish favor mosquito larvae, insects, crustaceans, worms, and fry, but are definitely known for eating tadpoles as well. They may occasionally feed on froglets or small frogs too. They aren’t picky as long as protein-rich food sources are readily available. This species prefers to explore in small schools, so your pond should ideally have a cluster.
A common issue with rearing pumpkinseeds in ponds is their tendency to breed. Without a predator, they can quickly fill up a pond, producing too much waste and competing with other species. They’re a great panfish to rear and breed if you have larger carnivorous species, such as largemouth bass, in a pond.
6) Crucian carp (Carassius carassius)
When seen for the first time, crucian carp can often look like giant versions of goldfish, which are likely to be their descendants on the genetic tree. Variable in shape, this species can change its morphology depending on the presence of predators. They can adopt a disc-like form, making it challenging for predators to swallow them whole. If only tadpoles could do the same thing in the presence of carp! This fish would swallow them in the bucketload if that were possible.
Crucian carp is not as commonly available as a commercial fish compared to orfe or koi. It is occasionally reared in garden ponds, but is more often cultivated in fish farms. It is a game fish in the UK, where it is frequently caught by rod and tackle. Despite its capacity to eat a wide variety of protein-based food, it is actually an omnivore that can survive on plant matter. If desperate, it will even eat sand and detritus. It subsists on just about anything organic, including algae and plankton.
In ponds, crucian carp grow to a maximum length of 6 inches (15 cm). They can be reared alongside close relatives, such as the common carp (Cyprinus carpio) and its subspecies. They tend to veer close to the pond bottom, where they can search for food. They can also be trained to receive floating flakes and pellets on the water’s surface.
7) Bluegill sunfish (Lepomis macrochirus)
A popular sport fish, the bluegill sunfish makes an appearance in almost all types of natural freshwater systems. They frequently remain close to the shoreline, in shallow pools with high structural diversity. Here, they roam around in small groups to feed and spawn. Their favorite food types include insects and small fish, but they will readily feast on tadpoles and frogs. The introduction of bluegills in garden ponds can wipe out frog tadpoles, making them an effective means of biocontrol.
Bluegill sunfish play an important role in the food chain as they pass on energy to many higher forms of life. They are desirable prey fish for bass, trout, large birds, otters, racoons, and even snapping turtles. Ornamental ponds with bluegill clusters should have a resident predator or be designed to attract a few. If left uncontrolled, this species can quickly breed to fill up the whole pond!
When protein-rich food sources are scarce, bluegills can shift to a plankton-based diet. In severe cases, they will eat their own eggs and larvae. Their location in the water is influenced by food availability. If food in the pond itself is scarce, they may remain close to the water’s surface, calmly suspended, until they spot an insect or two.
8) Smallmouth bass (Micropterus dolomieu)
The smallmouth bass is a powerful fish with excellent hunting skills. Due to its dark and dappled coloration, it can easily blend into natural features, only accelerating from a slow cruise to strike at prey once they are close enough. This tactic is called “flushing” and is more effective compared to ambushing prey. This capacity to accelerate quickly has made it extremely popular with sport fishers. Moreover, its preference for clean and clear water restricts it to high visibility regions where its behavior may be observed from the surface.
In the wild, smallmouth bass favor microhabitats where other panfish, such as pumpkinseeds and bluegills, are present. These smaller fish, along with crayfish, insects, larvae, and the offspring of conspecifics are all fair game. Adult amphibians and tadpoles are also ideal food choices. If you’d like to keep a smallmouth bass in a garden pond, its diet will have to be supplemented with live prey. The occasional tadpole simply won’t be enough to satisfy this top-notch predator.
9) Largemouth bass (Micropterus salmoides)
If the smallmouth bass can eat a few tadpoles at once, the largemouth bass can eat an entire cluster in just one gulp! Even breeding frogs will have to stay close to the shallows if they don’t want themselves and all their eggs to swim in a bass’ inhospitable belly. This fish can eat just about anything that wriggles in the water, even other fish and small mammals that are as wide as its head!
As it is an ambush predator and is most comfortable when hidden, a largemouth bass will require a sturdy form of shelter close to the bottom of a garden pond. Unless provided with live food, it may attempt to feed on slow-growing ornamentals, such as koi or goldfish. Try to rear self-sustaining populations of panfish for good measure.
Largemouth bass has been introduced outside of its native range due to its popularity as a sport fish. Its effectiveness as a predator has made it invasive in several freshwater systems. It can also endanger natural populations of economically important coldwater fish (e.g. trout, salmon). Before investing in bass as a means to regulate tadpole and fish populations, make sure to check on your locality’s restrictions. Moreover, keep in mind that this fish will require a pond depth of 4 feet (1.2 meters) at the very least.
Consumption of Toad Tadpoles
Some toad tadpoles emit a toxin that makes them unpalatable and poisonous to predatory fish. The common toad (Bufo bufo) and cane toad (Rhinella marina) produce bufadienolide toxins that protect them against vertebrates. Fish that consume their tadpoles, capable of synthesizing the same toxins, may spit them out or avoid them altogether once they get an initial taste.
Cane toad tadpoles may regulate their own populations by feeding on their unhatched egg clusters. They are able to detect the presence of other eggs via the very toxins that they produce. As they are immune to their own poison, they can consume the unhatched eggs without ill effects. This gives them a competitive advantage, allowing just the strongest and oldest of hatchlings to survive.
The fish listed above may occasionally consume toad tadpoles by accident, but they cannot be expected to help control populations. If you find these venomous critters in your pond, you may wish to fish them out as a safety precaution. Toad tadpoles are usually much darker and more solid in terms of color. They also tend to have a chunkier morphology compared to the larvae of other amphibians. All things considered, when present in limited numbers and in naturalized ponds, they can live in harmony with fish.
