Summer’s in full swing as we’re writing this, and we’ve already spotted several pea soup-textured ponds at backyard BBQs. Our friends and relatives are always asking us what we think are the best algae-eating fish for ponds! Our answer usually surprises them.
If this article’s cover photo looks a little too familiar, keep reading. We’ll tell you about the 8 best algae-eating fish for ponds, divided by climate—but first, a little about how to actually get rid of algae.
The best algae eaters for ponds are… plants?
We know you came here looking for fish recommendations, and we’ll give ’em to you. But we do want to emphasize the fact that when it comes to algae-busting, fish are by no means your greatest allies. Plants are, which is why we wrote a full article on using those to get rid of these pesky microorganisms.
We recommend you check it out!
There are two main factors that make fish less effective at pond algae control than plants. The first is the fact that plants absorb the nutrients that allow algae to thrive, while fish actually produce them. This is why adding too many fish will greatly exacerbate existing algae problems—pea soup texture guaranteed.
Secondly, most fish don’t eat nearly as much algae as pet stores like to suggest. They often only like one or two types of algae, or they’re actually omnivorous detritus feeders that may or may not lose their taste for greenery as they mature. Even online sources regularly recommend species that aren’t even actually algae eaters at all!
Plants, unlike fish, don’t just mechanically remove algae. Instead, they help prevent them from being able to thrive in the first place, blocking excess light, absorbing excess nutrients, aiding in oxygenation, and helping to keep the water cool.
Should you avoid fish entirely for algae-battling purposes? Not necessarily. But when you head out to the store to pick up some algae-eating fish, be sure to buy plenty of plants as well.
The Best Algae-Eating Fish for Ponds: Which match your climate?
Cool & temperate ponds: Frost expected
- Winter lows: Below 50°F (10°C ), your pond may ice over
- Examples: Northeastern & Midwestern USA, most of Canada, UK, Central/Northern Europe, much of Japan, New Zealand (South Island)
Tip: Don’t forget about pond depth in cold climates. It’s what protects your fish during frosty winters, so adjust accordingly.
✅ Koi (Cyprinus rubrofuscus ‘Nishikigoi’)
To us, there are few things more beautiful than a healthy pond dotted with lily pads, a multitude of colorful koi gracefully drifting along below the surface. It seems a lot of people agree, because koi are undoubtedly the #1 most popular fish for larger ponds.
And did you know that koi aren’t just pretty to look at, but also eat algae? These carp are omnivorous, but they’ll still nibble on pesky greenery, especially when other foods are scarce. Some folks find that hand-feeding their koi clumps of algae actually works pretty well!
Koi size is obviously a factor to keep in mind. Don’t try to keep these fish in smaller ponds: 1,500 gallons really is the minimum, with many pond enthusiasts upgrading when they realize even that’s not enough to house their growing koi collection. Filtration should be excellent—preferably double or triple what you’d normally use.
| Max. length | Up to 35″ (usually max. 25″) |
| Min. pond size | 1,500 gallons (300-400 gal per fish) |
| Algae-eating capacities | Not too bad |
✅ Goldfish (Carassius auratus)
Good ol’ goldfish are among the only algae-eating fish that will do well in smaller, cold-climate ponds. This clearly reflects in their popularity level: throughout most of the world, C. auratus is probably the most popular pond fish of them all. It’s also the oldest, with the first orange color morphs popping up over 1500 years ago in China.
Now, like koi (and most other fish on this list), goldfish are no “lean, mean algae-killing machines”. They’re omnivores that feed on a variety of foods. Still, most goldfish will nibble at algae from time to time, especially during wintertime when normal feedings should be reduced.
Also, keep in mind that goldfish are highly prolific. They reproduce quickly and can overrun a pond within a few years—you’ll have to keep their population down to avoid exacerbating any algae problems.
Tip: Double-tailed and deep-bodied fancy goldfish are a lot less sturdy than their single-tailed, torpedo-shaped cousins. They may survive light frosts, but are generally better suited to subtropical climates.
| Max. length | 8″ (fancy) to 12″ (common) |
| Min. pond size | 150 gal (fancy) to 250 gal (common), 40-60 gal per fish |
| Algae-eating capacities | Not too bad |
Fathead minnow (Pimephales promelas)
The fathead minnow is a popular feeder and bait species that, over time, managed to wiggle its way into pond keepers’ hearts. We think it more than deserves the credit it now gets: this species stays small, nibbles algae, and is native to the USA. Additionally, it’s hardy, doesn’t bother plants, breeds readily, and doesn’t mind its home icing over as long as the pond is deep enough.
As an added bonus, a xanthic (golden or pinkish) strain of fatheads, known as the rosy red minnow, is also available nowadays. Although they’re omnivores with a taste for many different foods (including detritus), these minnows do help keep algae in check. Give them a try—you’re unlikely to regret it.
| Max. length | Up to 3.5″ |
| Min. pond size | 40 gallons |
| Algae-eating capacities | Minor help |
Subtropical ponds: Mild winters
- Winter lows: Between 41–59°F (5–15°C), frost is uncommon
- Examples: Southeastern USA, Southern California, Mediterranean, South Africa, Southeastern South America, New Zealand (North Island)
Tip: You can keep all the coldwater fish mentioned above here as well.
American flagfish (Jordanella floridae)
Yes, they exist: fish that stay small, but do actually have a serious taste for algae. And the amazing thing is that, as their name suggests, American flagfish are 100% USA born and bred! We love a good native species—this one’s naturally found in Florida. And would you look at those stunning colors?
Flagfish are technically omnivorous, with a large portion of their diets consisting of tiny crustaceans and other critters. However, they do love algae as well. That includes some of the peskier types, like black brush algae—the only non-tropical species on this list that doesn’t turn up its nose at BBA.
Tip: Have an unheated pond that you worry will get too cold for your American flagfish? Being native Floridians, they don’t like the cold and will begin to struggle around 40 °F. You can consider bringing a few inside in an unheated aquarium each winter, just to ensure some always make it through the winter.
| Max. length | Up to 2.5″ |
| Min. pond size | 40 gallons |
| Algae-eating capacities | Pretty good |
Rosy barb (Pethia conchonius)
Unlike flagfish, which are the undisputed winners in the subtropical category, rosy barbs aren’t really algae-eating champions. They’re more like fathead minnows: polite, small, and do occasionally nibble at algae, making them overall pleasant fish to keep. Perfect for folks who don’t have mini lakes in their backyards—40 gallons should suffice for a group of ten or so rosies!
It’s important to keep in mind that, like flagfish, rosy barbs should be hardy enough to withstand temperatures down to 40 °F. However, this isn’t ideal for them, and casualties can happen. Move them indoors if winters are consistently chilly, or keep a pond heating unit on hand if you expect the occasional extra-cold night.
| Max. length | Up to 6″ |
| Min. pond size | 40 gallons |
| Algae-eating capacities | Minor help |
Tropical ponds: Year-round warmth
- Winter lows: Above 59°F (15°C) consistently, no frost
- Examples: South Florida, Hawaii, Caribbean, Southeast Asia, Northern Australia, parts of Central and South America
Tip: Some of the coldwater and temperate fish will thrive here as well, but not all of them. Check beforehand whether your intended choice can handle extended periods of heat.
Siamese algae eater (Crossocheilus oblongus)
What’s in a name? Well, quite a lot in this case! And the Siamese algae eater lives up to its denomination, at least when it’s still small. Along with the flagfish, this is the only species on the list that will touch black beard algae, and italso has a taste for rather unpalatable long strands of hair algae.
As always, there are unfortunately also two drawbacks. First off, Siamese algae eaters, like many fish, become more omnivorous as they age. Secondly, they really are true tropicals—if temperatures drop below 65 °F for a few days, they’ll stop eating algae and may even perish. Still, as far as the best algae-eaters for ponds go, this is one of our clear winners!
| Max. length | Up to 6″ |
| Min. pond size | 40 gallons |
| Algae-eating capacities | Great when young, not too bad when mature |
Bristlenose Pleco (Ancistrus sp.)
The armored catfish or Loricariidae, commonly known as Plecos, are a pretty darn big family of fishes. There are over 600 species currently recognized. Some eat algae, while others never touch it—or only like it when they’re young. Some are highly invasive and problematic, while others rarely cause issues. The bristlenose catfish of the genus Ancistrus are among the “good” Plecos.
Now, bristlenose catfish aren’t champion algae eaters by any means. However, soft brown and green algae do appear on their menus, so we can’t say they don’t play their part. As long as your pond stays above 65 °F (almost) year-round or is heated, these relatively small catfish can make a fun and useful addition to your pond cleaning crew.
| Max. length | Up to 6″ |
| Min. pond size | 40 gallons |
| Algae-eating capacities | Pretty good |
Molly (Poecilia sphenops)
Yep, we’re discussing a bunch of aquarium favorites in this section! For most people, keeping these fish is out of the question unless they set up a heated indoor tank. If you live in the tropics, however, you may be able to keep them in your pond. If you do, consider mollies!
Mollies are scientifically known as Poecilia sphenops, making them close cousins of the ubiquitous guppy (P. reticulata). These small livebearers are commonly kept for mosquito control, but they also have a taste for soft algae. Their suitability for small ponds, variety of color morphs (black, gold, speckled, and more), and quick reproduction makes them a fun choice, though do keep in mind they really don’t like the cold.
Did you know? The sailfin molly, P. latipinna, also loves eating algae. It does best in slightly brackish water, however, so it’s not the best choice for most regular ponds.
| Max. length | 4.5″ |
| Min. pond size | 40 gallons |
| Algae-eating capacities | Pretty good |
“Algae eaters” to avoid
🚫 Grass carp (Ctenopharyngodon idella)
Unless you have a huge, natural pond on your property, avoid grass carp. They grow huge, and they’re voracious for plants. Aside from turning our ponds into wastelands, they’re also invasive and cause serious damage to local waterways, so we actually forego them entirely ourselves. We prefer native fish species for ponds like these.
Yours truly can personally confirm the mayhem grass carp can cause in smaller ponds. My parents fell in the grass carp trap years ago, and although it was very cool to see them grow huge, the pond turned into pea soup at the start of each spring. It wasn’t until the carp eventually died off, reducing the massive bioload, that it stayed algae-free.
| Max. length | Up to 45″ |
| Min. pond size | 0.25 acre |
| Algae-eating capacities | Too good, will eat all your plants |
🚫 Common & sailfin Pleco (Hypostomus plecostomus & Pterygoplichthys gibbiceps)
If you live in a tropical area, one of the large armored catfish species, known as Plecos, may seem like a logical algae-eating choice. Look at that sucker mouth: what else could these guys eat?! The answer is muck. Loads of muck. They start out eating algae, but lose interest within the first few years.
If you’d like to keep a Pleco in your pond for entertainment value, there’s no problem in that. Although this is an invasive species that has wreaked havoc in waterways across the tropical USA, especially Florida, it’s not illegal to keep. Just don’t expect it to help clean algae—the adults’ significant bioload is more likely to exacerbate any problems.
Tip: Want a somewhat effective algae eater that doesn’t come with the risk of destroying your local streams if it gets out of your pond somehow (which can happen during flooding events)? We’ve already mentioned the solution above: if your climate allows it, you can try a bristlenose Pleco instead.
| Max. length | Up to 20″ |
| Min. pond size | 1,000 gallons |
| Algae-eating capacities | Alright when small, but quickly lost |
❓ Chinese hi-fin banded shark (Myxocyprinus asiaticus)
A quick look at pond forums reveals folks waxing lyrical about this suckerfish and its algae-eating capabilities. We often see this one sold as an aquarium fish, but it can reach over 4ft in length. The specimen pictured above is just a juvenile! Its size makes this species a rather unrealistic choice for indoor tanks—ponds of 2.500+ gallons do seem like a better option.
So, these “sharks” can do well in large, cold ponds. Whether they’re good algae-eaters, however, is debatable. Although they seem to like greenery when they’re still small, hi-fin banded sharks tend to begin preferring meaty foods like bugs, crustaceans, and carrion as they age. You shouldn’t buy one unless you’re prepared for it to stop eating algae entirely at some point!
| Max. length | Up to 40″ |
| Min. pond size | 1,500 gallons |
| Algae-eating capacities | Great, but decline/disappear with age |
❓ Mozambique Tilapia (Oreochromis mossambicus)
The latest smash hit in the pond world is Tilapia, which is actually a catch-all name for dozens of different species of cichlids found mostly in Africa. Some of these fish, notably the Mozambique Tilapia, are big algae aficionados.
Tilapia may be the best algae eaters on this list, but they’re also among the least feasible for the casual backyard pond keeper. Depending on the species, they don’t do well below 50-60 °F, which would mean most people need a heated or greenhouse pond. Additionally, Tilapia are voracious plant eaters, need quite a bit of space, and are banned in many areas due to their invasive nature.
You could keep Tilapia if you have a larger, lake-ish type (fishing) pond and like to eat fish, or set up a dedicated mini farming operation. In colder areas, you’d stock the fish once temperatures reach a consistent 50 °F or so, and then harvest for consumption after summer. In warmer regions, you can remove fish as you see fit.
| Max. length | 15″ |
| Min. pond size | 1,000 gal for farming, 2,000 gal for casual |
| Algae-eating capacities | Too good, will eat all your plants |
Conclusion
Although fish aren’t the most useful allies in the battle against pond algae—UV units and especially plants are much more effective—they can play a role in a healthy mini backyard ecosystem. Many species are advertised as “the best algae-eating fish for ponds”, but few actually have a taste for green muck; the ones on this list range from okay to good.
Struggling with algae in your backyard pond? Or maybe you’re still dreaming of your own outdoor mega fish tank? We can help. FantaSEA Aquariums also offers pond support! Contact us to let us know how we can assist.
Sources & further reading
Yao, Y., Zhang, M., Tian, Y., Zhao, M., Zeng, K., Zhang, B., … & Yin, B. (2018). Azolla biofertilizer for improving low nitrogen use efficiency in an intensive rice cropping system. Field Crops Research, 216, 158-164.
