This is not uncommon: everything is going according to plan in your pond when, seemingly out of nowhere, algae starts rearing its ugly head.
Thankfully, I’ve been there before and so decided to give you a few ideas for algae eater fish that could do the cleaning work for your outdoor pond.
Typically, fish that eat algae as their primary diet don’t do well in cold water and rough winters.
Through my research and experience, I’ve found that the best choices are usually omnivorous species that can tolerate very cold temperatures.
Some do better than others but whether these creatures can be used to clean your ponds will largely depend on your local climate.
That being said, let me show you 7 algae eater species that could work wonders for your pond.
7 Algae Eater Fish for a Clean Outdoor Pond
When researching for this article I made sure to pick resilient fish and other creatures that have been seen to consume large amounts of algae.
However, keep in mind that these omnivores are usually opportunistic feeders, which means that they will also eat bugs and whatever else they can fit in their mouths. For this reason, you’d want to feed them sparingly if not at all to encourage them to consume more algae. This is because, more often than not, algae will not be the primary food choice of such fish.
Also, some fish prefer to eat a certain type of algae over others.
Here are some examples of different types of algae that could grow in a pond:
- Filamentous algae;
- Aglae films and surface algae;
- Single-celled algae (green water);
There are species that will eat the first two types. Most of them would prefer the filamentous algae which is similar in texture to the black algae we fight off in our aquariums.
However, if you have issues with turbid green water, you should simply get a UV water clarifier, since no algae eater would take care of that in a pond. You can visit this article of mine and check the stronger units I discuss as viable solutions or have a look at one such option directly here (the 18 and 36-Watt ones).
That being said, have a look at some of the good algae eater fish for a clean pond:
1. Mirror Carp – Cyprinus carpio carpio
by Sam Stukel (USFWS), Gavins Point National Fish Hatchery
The Mirror Carp, also known as Israeli Carp, is an omnivorous fish that has been known to forage for algae. Typically, these fish grow fast and reach up to 25 inches (63.5 cm) in length which is why they work best in large ponds.
The Mirror Carp fish will chew on filamentous algae and will do so way more than Koi and Goldfish (mentioned further down in this article).
The caveat here is that the carp needs to grow large enough to make a dent in your pond’s algae. It’s unrealistic to get a small fish and expect it to eat all the algae.
On that note, you should not get too many because of the Mirror Carp’s impressive adult size and quick growth rate.
Anyway, what I like about the Mirror Carp is that it tolerates a wide range of temperatures and has no issue with overwintering outdoors.
If you have a decently-sized pond you could introduce a specimen or two without worrying about a winter kill.
Mirror Carps are also very personable and may even learn to feed from your hand.
However, I recommend letting these fish eat the algae before teaching them that.
Author’s note: Before we move on, I need to make a quick clarification as to which carp is which. To spare you some headaches I will tell you that the Mirror Carp is a genetic variation of the Common Carp.
by Sam Stukel (USFWS), Gavins Point National Fish Hatchery
The Mirror Carp is just a selectively bred Common Carp that serves slightly different purposes, in the context of aquaculture.
- What it eats: Filamentous algae
- Temperature range: 32 to 95 °F (0 to 35 °C)
- Maximum size: Typically 25 inches (63.5 cm), but it’s not unseen for a Mirror carp to reach 3 feet (90 cm)
2. Chinese High-Fin Banded Shark – Myxocyprinus asiaticus
The Chinese High-fin Banded Shark is a large freshwater fish that feeds predominantly on algae. It thrives in frigid temperatures and is a good addition to a well-oxygenated Koi pond.
Caution: Because of its name, some people may confuse this fish with the Chinese Algae Eater. The Chinese Algae Eater is rather aggressive and only eats algae as a juvenile. I would never put a Chinese Algae Eater in a pond with other fish because it will try to eat their slime coat.
Anyway, before thanking me for showing you this fish, know that the Chinese High-Fin Banded Sharks do need a lot of vegetation in their diet.
These fish will feel very comfortable grazing all of the algae in your Koi pond but will need algae wafers once their habitat is clean.
Also, the Chinese High-Fin Banded Shark is technically an omnivore and likes to have some crustaceans and other insects occasionally.
Anyway, to clear any misconceptions, this fish will not be able to survive the winter in a pond that freezes solid.
The opposite should also be considered.
I would not try to get my hands on a Chinese High-Fin Banded Shark if the summer gets really hot where I live.
These creatures originate from mountain streams and enjoy precisely that – cold fast-flowing water.
The high-fin sharks feel best at temperatures of between 59 and 68 °F (15 to 20 degrees Celsius).
However, these algae eaters can tolerate and will be okay in cold water with a temperature in the 40s (between 5 and 10 °C).
I’ve found that as long as you keep your pond aerated and it doesn’t get completely covered in ice, the Chinese High-Fin Banded Shark will live to see another year.
Author’s note: One thing I find interesting with this “shark” is that most people agree it gets uglier with age. Young Chinese Banded Sharks have stripes and a relatively large dorsal fin. However, with age, they lose the stripes, become more elongated and the dorsal fin stops growing long before the fish itself.
I don’t get bothered by this as much as I like these peaceful giants, but it may be important to some.
Here’s how an adult looks like:
Anyhow, the Chinese High-Fin Banded Shark still remains a shark look-a-like in its adult years. In fact, enough so for me to include it in my article about shark-looking freshwater fish.
- What it eats: Filamentous algae, surface film algae
- Temperature range: Feels best at 55 to 75 °F (12.7 to 23.8°C) but can tolerate temperatures in the lower 40s °F (5 to 10 °C)
- Maximum size: Typically 2 feet or 60 cm but some specimens have been recorded to reach 50 inches or 127 cm
3. Goldfish and Koi- Carassius auratus and Cyprinus rubrofuscus
The only reason I’m talking about two different fish species in the same section is because they are very similar to one another in the context of cleaning ponds from algae:
Both the Goldfish and the Koi are fish that will eat algae alongside snails, insects, worms and some other plants. However, these fish will not be the best algae eater in your pond because algae is not their first food of choice.
So why would I bother listing them here then? Two reasons:
- Most people already have them or want to have them in their pond;
- They will turn to more algae grazing if they are being fed sparingly.
If your garden pond has a serious algae problem and has a couple of Koi and goldies in it, you could just reduce the feeding.
I’ve found that feeding smaller amounts every 3 days works for encouraging algae grazing.
Anyone who has kept a Goldfish knows that it’s a challenge to select live plants for its habitat because the fish likes to nibble at them.
Author’s note: You’ll not be “forcing” your fish to eat the algae through starvation. Koi fish and goldfish are opportunistic omnivores and would do the same in the wild if other food was not available. The stomachs of these fish are suited for extracting nutrients from vegetation.
Anyway, I would not expect Koi or Goldfish to get rid of a heavy hair algae infestation quickly.
The process will take time and it will depend on how well your pond is stocked.
- What they eat: Filamentous algae
- Temperature range: Down to freezing temperatures but the optimum range would be between 65 and 75 °F (18 to 24 °C)
- Maximum size: Around 35 inches for Koi and 15 inches for Goldfish (around 89 and 38 cm, respectively)
4. Central Stoneroller – Campostoma anomalum
by The Fishes of North Carolina – NCfishes.com (if not BDR57)
The Central Stoneroller is fish, native to North America, and has a diet that consists of 95% algae.
Though these fish seem the ideal choice as algae eaters for a small pond there’s a caveat to keeping them.
The caveat is that your backyard pond should be able to provide them with stream-like water movement.
They inhabit river creeks and don’t do well in waters that move too slow.
Also, Central Stonerollers prefer clean, well-oxygenated water and are known to not tolerate too much debris.
Anyway, this fish is an algae-eating machine and will pretty much try to forage the stuff all day long.
This type of Stonerollers will likely gulp the occasional worm or insect but will prefer to eat filamentous green algae most of the time.
So much so, that I would pay attention to the overall algae growth in the pond and make sure to provide algae wafers when the former is not abundant enough.
Anyhow, the Central Stonerollers don’t grow much, and only reach a maximum size of around 6 inches (15.24 cm). For this reason, I would not advise keeping this species alongside large predatory fish.
As for surviving a cold climate – Central Stonerollers will have no issue with that if the winter is mild where you live.
As long as the water keeps moving and the temperatures don’t drop below 40 °F (5 °C) your Stonerollers will be fine.
Overall the Central Stoneroller can be an excellent algae eating fish to clean a pond, but some very specific conditions are needed.
- What it eats: Filamentous algae, brown algae
- Temperature range: 41 to 65 °F (5 to 18.33 °C)
- Maximum size: 6.7 inches or 17 cm
5. Common Pleco – Hypostomus plecostomus
I only included the Common pleco because I see it being recommended way too often for an algae eating fish that may not be your cup of tea.
There are a few things that I need to tell you about this catfish before you decide to add it to your pond.
First of all, these pleco species only eat algae in their juvenile years.
After that, they move to a different kind of diet and do poorly as algae eaters. It’s no wonder aquarists use different pleco species for cleaning algae in home aquariums.
Secondly, the Common Pleco becomes very aggressive in adulthood, so keep that in mind if you have timid, non-aggressive pond fish.
Finally, Hypostomus plecostomus is more of a subtropical fish, rather than a cold water one. They don’t do well in temperatures lower than 65 °F (18 °C).
If the weather stays relatively warm year round where you live then you may have a chance of keeping your pleco alive in the pond.
You can also opt to transfer your Common pleco inside during a colder winter, but these fish are agile and almost impossible to catch in larger ponds.
And since I’m at it – the same applies to the Siamese Algae Eater, which I see being recommended by other blogs for some reason.
Author’s note: Even if your pond is small and you’re able to catch the pleco, you should take into account their adult size, which is close to 25 inches or a little over 60 cm. This means that you can’t house an adult Common Pleco in a 40-gallon aquarium for a couple of months during the winter.
Suggested Read: How Big Do Different Plecos Get? (Adult Size Resource)
Personally, I would not put a mature common pleco in any tank under 150 gallons, but the bare minimum is considered to be around 90.
Anyway, I would say that the common pleco can be a good algae eater for your pond, but only when certain very specific conditions are met.
- What it eats: Filamentous algae, surface film algae
- Temperature range: 65 to 82 °F or 18 to nearly 28 °C
- Maximum size: Typically around 25 inches (63.5 cm)
6. Tilapia Species – Oreochromis spp.
The Tilapia are voracious cichlids that will clean larger ponds from filamentous algae. These fish multiply fast and work best in ponds where their population is controlled by a predatory species such as Bass.
If you’re the owner of a ¼-acre or larger outdoor pond, then I would strongly recommend considering the Tilapia as a form of natural algae control.
When I first saw the impact of these fish, I was very impressed by the amounts of filamentous algae they were consuming.
Soon after they establish, they’ll start devouring the stuff. I would stock 20 to 30 pounds of tilapia per acre of farm pond.
Anyhow, you could choose between multiple species of Tilapia, but I recommend either getting a Blue Tilapia (Oreochromis Aureus) or the Mozambique Tilapia – Oreochromis mossambicus.
The former grows to about 8 inches and has a higher cold tolerance whereas the latter grows to about 11 inches and does not tolerate cold water well.
Keep in mind that there’s a good chance you’d end up with a hybrid Tilapia, so there may be some variation in their maximum size and hardiness.
Author’s note: Typically, Tilapia will start showing health issues at a water temperature of around 55 °F or 12.7 °C. Following these thoughts, I’ve found that you’ll start seeing fish kills at around 50 °F (10 °C). Expect your Tilapia to die off completely if you live in the Northern part of the US.
Anyway, Tilapia is one of the best and most efficient pond-cleaning algae eaters on this list.
However, what makes them even better is that they are excellent forage fish.
In my observations, stocking on some Tilapia in a bass pond will sustain a healthier and larger bass fish.
This is because Tilapia are very prolific and spawn multiple times throughout the year.
Small tilapia are easy prey for, say, Largemouth Bass and the population of the algae eater is kept under control.
Essentially, I perceive it as if I’m feeding filamentous algae to my largemouth bass. The Tilapia eradicate the algae, and the bass fish eat the tilapia.
A good scenario would be one where you introduce tilapia in a bass pond overgrown with algae down in Texas.
Finally, you can actually fish and eat these fish which makes for a more exciting end of season.
- What it eats: Filamentous algae, lots of it
- Temperature range: 68 to 86 °F for optimal growth (20 to 30 °C); fish deaths will occur at 50 °F or 10 °C
- Maximum size: Up to 15 inches, depending on the species of Tilapia (up to around 40 cm)
7. Japanese Trapdoor Snail – Viviparus malleatus
In my bonus entry which is not a fish, but technically among the best algae eaters for a outdoor ponds, I list Viviparus malleatus:
The Japanese Trapdoor Snail is the preferred choice as an algae-eating pond snail because it does well in winter and doesn’t take over too quickly.
Though these omnivorous freshwater snails are very good at eating algae, I need to point out that they won’t be able to eradicate the growth completely.
I would recommend adding a couple of Japanese Trapdoor Snails only if your other algae eaters need a little help in controlling the unwanted growth.
A plus here is that the snails won’t eat healthy pond plants.
Anyway, from what I’ve seen Koi fish and pond loaches can make short work of these snails.
It’s not unseen to load a bunch in your koi pond and end with empty snail shells soon after.
What the pond owners I know like about this snail species is that it is a livebearer.
This is highly appreciated if you don’t want snails that reproduce too quickly and become a pest.
An interesting thing about the Japanese Trapdoor Snail is that, same as with Mystery Snails, it will try to float away when the water becomes contaminated or too dirty. This makes the surfacing snails a good indicator of water quality in a pond.
Finally, this is likely one of the very few snails that are able to survive winter in the Northern regions of the United States.
Their ability to eat algae plus their hardiness is why other pond owners and I love them.
- What it eats: Biofilm and surface algae, filamentous algae (if not too hard)
- Temperature range: Prefers 68 to 85 °F or 20 to 30 °C, but is hardy enough to survive winters
- Maximum size: Up to 3 inches (7.6 cm)
Are there ways to clean your pond without adding algae-eating fish to it?
Although adding reliable algae-eating fish to your pond can be a good natural approach to cleaning it from unwanted growth, there are other methods that I’d like you to consider.
Algae is not actually a problem, but rather the result of too many nutrients available in the water.
One of the best ways to put these nutrients to work is by adding more plants to your outdoor pond.
Specifically, I mean adding floating plants, because they act like nutrient sponges:
Floating plants have access to atmospheric Carbon Dioxide which, combined with the abundance of nutrients in the water, is a recipe for explosive growth.
Fast growth means fast depletion of excess nutrients in the water.
In my experience, adding some floating plants to your pond is one of the best methods to keep it algae-free.
Anyhow, researching a couple of floaters and making sure they are legal in your area (some species get invasive) is the first step here. You can check some ideas or floating plants in my list over here. Eventually, the floating plants will outcompete the algae.
Anyway, other sources of excess nutrients in ponds I’ve found are:
- Overfeeding your fish;
- Overstocking with fish that produce a lot of waste;
- A weak biofilter which leaves too much Ammonia or Ammonium for the algae to feed on;
- Too much direct sunlight over the pond;
- Fertilizers leaking from the surrounding area.
I’d try to figure out what may be causing the algae growth in my pond and then evaluate from there if I should add some algae eaters.