List of Plants Toxic to Pond Fish (Common Poison Species)

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Guide to Plants Toxic to Pond Fish, Koi & Goldfish 2019 (Poison Species)

As well as sharp points, many plants, such as the Acacia tree, will produce toxins as a defense mechanism to deter wildlife.

To protect themselves from being consumed, many plants produce toxins or secondary chemicals that may be toxic to some organisms, including pond fish. For example, acacia trees in Africa produce a compound called tannin, which is moderately toxic to organisms, including giraffes (the main browser of acacia trees, due to their long necks). In fact, upon being munched on, the leaves of acacia trees will emit warning pheromones (ethylene gas, specifically) to any trees downwind, alerting them to start producing tannins as well.

Many other plants, including those possibly around your pond, have similar defense mechanisms in place.

Some plants simply have poisonous leaves, berries, or root systems. Others, like Deadly Nightshade, are almost entirely toxic.

Some may only have poisonous leaves, others may only possess toxic compounds in the roots, and others may be entirely toxic, leaves, shoots, roots, berries and all (nightshade, for example). Many are only toxic to certain organisms, like humans or dogs, and others are only toxic to fish (called ichthyotoxic) or insects, others may only impact other plants to reduce competition, and still others are poisonous to just about everything. You certainly don’t want these sorts of plants in or near your koi, goldfish, or fish pond, as they could cause your fish to become ill, act oddly, disrupt metabolism, or even cause death in some extreme cases.

Here we will list a variety of plant species, both terrestrial and aquatic, that are toxic to fish to aid you in deciding which plants to avoid planting around ponds.

List of Common Plants That Are Toxic & Can Poison Pond Fish (Updated)

This list is by no means exhaustive, but rather covers some of the more common plants (with a few less common ones mixed in) that are often either naturally occurring or sought after for garden ponds. You should certainly conduct further research before incorporating any plant in or around your pond to ensure it’s safe for fish.

Common Toxic Aquatic Plant Species

Blue-green Algae

While not actually a plant, it’s important to mention blue-green algae, also known as cyanobacteria, as it’s potentially quite harmful. As the names imply, blue-green algae is bluish green in color (cyan) and composed of bacteria, not algae, though it does closely resemble algae when it blooms out of control. Cyanobacteria contain a host of harmful toxins, and different species have different dangers. While the presence of some cyanobacteria is natural and even beneficial (as covered in our article on the different types of algae), if a cyanobacteria bloom occurs it can cause muscle degeneration, oxygen depletion (and asphyxiation as a result), damage the internal organs such as the liver and kidneys in addition to damaging the gills, and ultimately can result in mass fish kills.

However, the smaller the water body is, the easier it is to monitor and control blue-green algae. Simply conduct water quality tests on a daily basis to monitor nutrient levels, pH, dissolved oxygen levels, and so on. If your pond has low dissolved oxygen and high levels of nutrients such as nitrogen, you’re at risk for a cyanobacteria bloom. Simply return the water to normal, healthy parameters and the bacteria will be kept in check.

Common Toxic Tree Species

Though naturally occurring around much of the world, oak species contain compounds known as tannins that, while they likely won’t cause death, they can cause digestive upset and reduced digestive rate. Specifically, the leaves and acorns of oaks contain tannins, and can make your fish sick if they fall into the pond where they are able to be consumed. As well as this, the acorns and leaves are prone to build-up and will cause issues with water condition if large quantities are left to decompose on the pond floor.

With their ability to either be pruned into a shapely shrub (say, one that looks like an animal or statue, for instance) or trained into a mature tree with large swooping branches and fragrant needles, some pond owners enjoy having yews leaning over their water.

However, the needles and seeds are both poisonous to fish due to taxine alkaloids, though interestingly enough the berries themselves are edible (so long as the seeds are not consumed). The Japanese yew (Taxus cuspidata) is particularly dangerous, as it’s also an invasive species in Europe and North America.

Cherry (Rosaceae Prunus – all species)

Though cherry trees are certainly beautiful with their fragrant and vibrant blooms and bright fruit, be they wild black cherry, pin cherry, choke cherry, or modern cultivated cherry, all parts of them are considered toxic to fish. They belong to the rose family and are highly sought after by gardeners and enthusiasts alike for their appearance, scent, and edible (to humans!) fruit.

However, all parts of cherry plants are toxic to fish, and the seeds (or pits) in particular contain hydrocyanic acid, also known as prussic acid. In larger animals, such as humans or livestock, these pits would have to be consumed in great quantities to have much effect. In fish, however, consuming just one or two pits could cause death. Hydrocyanic acid blocks the ability of tissues to use oxygen and ultimately results in suffocation, spasms, and death shortly after.

Similar to cherries, peach pits also contain hydrocyanic acid. In fact, anything in the genus Prunus (also known as drupes or the stone fruits, named after their hard pits), should be avoided near your pond. This includes apricots, plums, nectarines, mangoes, and so on.

All parts of peach trees are toxic to fish to varying degrees, though only the pits and the seed inside of them may cause death if nibbled on. The leaves, buds, etcetera have only been known to cause little to no effect.

All portions of black walnut are toxic, except for the meaty walnuts themselves. The leaves, roots, bark, and walnut husks (also known as modified bracts) that surround the nut and its shell all contain something called juglone toxin, which incites cellular death in plants (making walnuts exceptional at killing off competing plants around them), insects, and small organisms like fish if the plant matter is consumed. The toxin is also leached into the soil via the root system, so if you’d like to have a walnut, plant it far away from your pond. Contrastingly, if you have an existing walnut tree and are looking to have a pond, place the pond far enough away from the walnut that it won’t pose a threat (there’s not much sense in cutting down a tree if you don’t have to that does have positive wildlife value and can provide you with food – the walnuts themselves are not toxic!).

Common Toxic Shrub Species

Jasmine (Oleaceae jasminum)

Typically occurring as flowering vines or shrubs, some jasmine varieties can also be evergreen. With their exotic, extremely sweet fragrance and attractive five-merous white flowers, placing jasmine by your pond can be tempting. However, the berries (and some argue the flowers as well) are dangerous to most wildlife and fish, causing disruption of the nervous system due to the presence of glycoside and hepatoxins.

Nightshade (Solanaceae solanum)

As might be expected from its name, all parts of nightshade are fatally toxic. Nightshade species are in the family Solanaceae, and in fact all members of this family should be avoided. They often have pretty and fragrant flowers and tasty-looking berries, but don’t be fooled – most types of nightshades are still considered dangerous to humans, livestock and fish alike.

In particular, the infamous Atropa belladonna, or “deadly nightshade” (pictured), which is in the same family as potatoes, tomatoes, and eggplants, has berries which are extremely toxic to organisms if ingested.

Alocasia (Araceae Alocasia)

Alocasia are very large-leaved tropical to subtropical plants, also known as the jewel plant for the beautiful patterning on their leaves. They’re often used by gardeners and ponders alike, as they effortlessly provide a tropical feel and don’t require much care so long as your temperatures average above 60°F year round and they can get plenty of moisture either from the soil, rainfall, or supplemental watering.

Their beautiful appearance aside, alocasia stems and leaves are toxic because they contain indigestible crystals of calcium oxalate, like taro mentioned below.

Taro, also known as elephant ear, is a subtropical to tropical flowering plant with impressive leaves that can be larger than a person! You may be a bit surprised to find this plant on this list, as it’s sold by many pond plant sellers and has been incorporated into many pond scenes as they add a tropical, exotic vibe. However, all parts of the plant are toxic to fish (as well as humans, dogs, cats, and likely many other organisms) if ingested due to the presence of insoluble calcium oxalate acid. Some pond owners may argue this, as they’ve had the plant without issue. Regardless, we recommend staying on the safe side and not having this plant in close proximity with your pond, but at least far enough away that there’s no danger of leaves falling into the water and your fish nibbling on them.

Wisteria (Leguminosaea Wisteria)

Wisteria is a beautiful, vigorous woody vine that can become a shrub or even trained to be a gorgeous viney tree. With dramatic, elegant drooping clusters of flowers that range from blue to purple to white to pink, wisteria can be quite tempting to add next to your pond as it provides a very magical feel. However, the flowers are known to be toxic to most animals, and so if it’s planted too close the flowers could either fall in or be blown in by wind if the plant is further away. The seeds are also toxic and can result in illness or death. Belonging to the legume family, most others in this family should also be avoided.

Common Toxic Flower Species

Bird of Paradise (Strelitziaceae Strelitzia reginae)

Though an extremely beautiful and unique plant, the leaves of the bird of paradise (native to South Africa) contain tannins. These aren’t deadly, but can cause illness and discomfort if they’re allowed to build up. The seeds, however, contain hydrocyanic acid, and like cherry will result in suffocation and ultimately death if ingested. Try your best to keep these plants far from your pond, or even avoid them altogether if possible.

A relatively common flower, as it’s both pretty and easy to grow (it’s able to grow in nature just fine on its own), tiger lilies should also be avoided. All parts of it contain Lycorine alkaloids, which don’t typically result in death unless ingested in large quantities, but most often cause nausea, convulsions, and inability to properly synthesize proteins in the body until the toxin has been diluted and exited the body. These symptoms have been reported in cats, dogs, and horses that have ingested Lycorine alkaloids via tiger lilies, daffodil bulbs, or other plants containing the alkaloids, and are likely to have similar effects on fish.

Morning Glory (Convolvulus/Ipomoea)

With deep green, creeping vines that sport lively blooms that open up each morning, morning glories are often planted on trellises or near things that they can climb around. Because of this as well as their white, blue, purple, magenta (or any mixture thereof) flowers, they make quite a pretty addition to water scenes. The seeds of morning glories (and of most things in the Convolvulaceae family), however, contain a chemical quite similar to LSD, called “natural LSD”, that is harmful to just about anything that ingests it. If any part of the plant is consumed, you may notice your fish acting oddly (because the effects are similar to that of LSD), refusing to eat, and producing excess waste.

An exceptionally pretty plant that grows several feet tall with showy, bell-shaped brightly colored flowers of all shades that are also uniquely patterned on the inside, foxgloves can be hard to resist, for they make a gorgeous addition wherever they are. With that being said, all parts of the plant are considered toxic to humans, dogs, deer, and fish alike (along with many other organisms) if the plant is in any way ingested. Consumption results in the heart rate slowing down dramatically or becoming irregular, and if too much is eaten then the heart can stop altogether. In fact, the cardiac and steroid glycosides present in foxglove act similar to medications used to treat tachycardia. You can plant it if you wish, but try your best to keep it away from your fish and any other pets!

31 thoughts on “List of Plants Toxic to Pond Fish (Common Poison Species)”

  1. I have a couple of floating planters in my fish pond. I would like something flowering but low growing. Are purslane, Vincas or Calibrachoas poisonous to goldfish?

    • Hi Chris,

      It’s difficult to say for many plants as there are very little studies available on their individual effects on fish, but it appears that the families of Apocynaceae (containing Vincas) and Solanaceae (containing Calibrachoas) contain some species that have shown possible piscicidal (poisonous to fish) properties –

      Again, this is just a single study representing just a few genera within the families, so it may not apply to your chosen species. However, I do know that these plants contain alkaloid compounds (most plants do; just to different degrees), which can indeed be toxic to fish, but they do need to be in high concentrations to cause serious harm. If your pond is fairly large and well maintained (i.e., good water quality), just a few floating planters are unlikely to cause major issues, especially if you make sure to clean away dropped foliage before it can leech into the pond water.

    • Hi Jim,

      Sadly, there is very little information on this pathogen and its toxicity to wildlife, so I can’t really advise here. Omitting any direct toxicity, at the very least, any apples (and by contrast, fungus), that land in the pond will certainly decay and have the potential to cause water quality issues if they’re in large enough numbers.

  2. I have Camellia’s close to my pond and a lot of their flower petals end up in my pond. Might these be toxic?
    I also have a large Photinia shrub next to my pond that drops a lot of leaves, especially the red ones, and ultimately blossom into my pond. Are these known to be toxic?

    • Hi Bernie,

      As mentioned in another comment above, almost all plants contain, to various degrees, compounds that can be potentially harmful to fish. In most cases, so long as you can remove the dropped foliage to prevent it leeching into the water, you shouldn’t have too many issues. However, we can still try to make a distinction on just how potent these compounds may be in different species and if the species has any unique properties that make it stand out.

      In terms of Camellias, it appears that some within the family (namely, “Camellia sinensis” – the tea plant!), have been identified as poisonousness to fish –

  3. Have an aquaponic system that is infected with roorknot nematodes. Seems sesame oil can kill the RKN’S, but cannot find much information about sesame’s toxicity to fish, specifically tilapia. Wondering if you know anything about the subject.

    • Hi B.H,

      Unfortunately, I don’t have any personal experience using sesame oil when it comes to fish, nor did my research on the topic turn up any information that might be helpful. Sorry about that!

      If you happen to discover anything in future, whether that be through research or your own experimentation, I’d be very interested to hear the results.

  4. Hi

    We have recently had all our pond fish die and I am wondering if it might be due to hemlock, which has invaded the banks and island.

    Any thoughts?


    • Hi June,

      What type of fish do you have, and how big is the pond? Also, have you performed any water quality tests recently? Although the hemlock could be a problem, it may not be due to direct toxicity, but more so a build-up of dead vegetation contributing to waste substances, such as ammonia. If pH readings are high (or fluctuating), and the weather is also hot where you are, ammonia can become particularly toxic to fish and other organisms and cause major issues within a short space of time.

  5. I would like to decorate my tank with privet plants but I don’t know if they are toxic to my tinfoil barbs and ruby sharks I’m not intending to put them there as food but to give my tank a more natural look but inevitable the fish will gnaw at them. Privet plants are beautiful garden plants but would also add beauty to my tank. What can I do please?

    • Hi Marian,

      I think the safety of this would depend on how often you could remove dropped fruit and foliage from the pond before it has a chance to decompose and cause issues with water quality. I think having grapevines certainly sounds pretty, but it would also require a lot of work and on-going maintenance, so you would probably need to take that into account before making a decision. Dropped foliage is also usually less dangerous (and easier to remove) compared to most fruits which can sink, and you definitely do not want a large amount of grapes decaying in your pond as that would lead to all sorts of problems!

  6. I have an almond tree dropping fruit and leaves in my pond I have had 3 fish die so far. My pond is greenish yellow right now and I’m afraid more fish will die. I have some over 2 feet long. Help

  7. Hi there. I have a suitable spot for a pond in Dorset, UK, that would be partly beneath the branches of a eucalyptus tree. Would fallen leaves from the tree create oil that would poison the pond? I would of course fish them out when they fall or use a net in leaf-dropping season. And there would be no fish in the pond, just wildlife.

    • Hi Chris,

      I believe that some (if not all) species of eucalyptus are considered toxic due to the high levels of polyphenols in the leaves, but whether this has the potential to harm wildlife or not will probably depend on the concentration of substance in the water and the amount of ‘leeching time’ the leaves have before you’re able to clean them out. If you’re able to clean the leaves out regularly, or if very little leaves fall in the pond, you may not have any issues. However, I’d probably advise against this if there was significant leaf fall or if you intended to have sensitive fish in future.

  8. Coincidence? I had a blue phantom pleco die after goong on a binge of eating water wisteria leaves. Is water wisteria toxic? Thanks

    • Hi John,

      That’s unfortunate to hear, but I don’t think water wisteria shares the same toxic properties as it’s terrestrial-named counterpart, and I couldn’t find anything from my research to indicate it has any toxicity worthy of note.

      Was your pleco displaying any other symptoms or behaving oddly prior to this?

  9. We had a bumper crop of apricots this year and some dropped off and rolled into the pond. I got them out when I could but the lilies are really thick hiding them. We had one 18″ koi die and he looked fine when I took him out. Now I have another about 22″ that I’ve noticed getting thin and she is usually very plump. It appears as if she is starting to bend horizontally. We have one white comet that we thought was dead back in April it is bent and looks like a dead fish floating when he is relaxing on top of the water. However he does get up some speed and eats before he disappears under the pond lily leaves again. I don’t know if the apricots are hurting them or there is something else. I don’t expect to see the one koi alive much longer. I have 7 more large koi and about 20 other goldfish born in the pond over the years. The pond is about 2000 gallons the pumps through two 55 gal filter drums into a smaller pond then overflows down a stream bed into the larger pond with the fish. We’ve had most of the large koi since we built it in 2006 since they were tiny and it pains me to see them get sick and die now. When we were working on the filters and replacing the filter box the hoses were going directly into the top pond and twice the raccoons chewed on the hoses and dragged them out of the pond causing the lower pond to be almost completely empty so there has been two complete water changes about 6 weeks ago. Any ideas?

  10. hi can any one tell me will ground ivy growing into my pond harm the fish or water there is a lot all down a 30ft side i have left it as the fish like laying in it and frogs ect sit on it and use it to get in and out thanks

  11. I have a Datura tree growing near my pond and some leaves fall in the pond and my after a while my fish die
    Would this be the problem?

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