In this article, we will be discussing the best fish to eat algae in your pond and how to decide the best fish for your pond’s unique conditions.
Many factors will change your choice and by using the information about each fish you can match up your pond type with the descriptions.
Start by thinking about your average year-round temperature. You’ll find some fish are better suited for a warmer climate and will not survive, while others will need extra care to survive a cold winter.
Consider what type of algae you are experiencing, how much there is to remove, and where that algae is most present, to help inform the best type of fish that will feast on algae in your pond.
Think about the fish that are already inhabiting the environment and your pond size. Will your small pond be able to accommodate larger fish as they grow bigger? Do you need to consider buying more algae eating fish for your large pond? Remember, adding too many fish decreases the amount of available oxygen and hurts the environment.
From our research, the following 6 pond inhabitants in this article (one is a snail), could be great new additions to your pond family, that will also have a hunger for algae!
Let’s take a moment to discuss the good vs. the bad algae, before we explain our favorite algae eating fish, we must first build a foundation on why we encourage the use of natural pond care.
It is perfectly normal to have some algae in your pond. In fact, algae is important when you want to manage a natural pond cycle. By using a mixture of algae eating fish, natural pond care practices, and a rake or shovel, you will be able to create an environment that is thriving by using the natural biological cycle for long-term success.
When you grow diatom algae (the good algae!), you are growing one of the most common types of microscopic food / power cells in your pond. This good algae converts nitrogen, phosphorus and carbon dioxide into oxygen-rich organic compounds, that create a healthy ecosystem. With a low amount of diatoms, you can cause serious issues in your pond’s balance.
Using a natural approach, has many long-term advantages over using a different model, like a UV light or algaecide, to control pond algae.
Not all algae is good for your pond… Beyond looking ugly, blue and green algae types are harmful because they reduce photosynthesis in your pond, which will harm the zooplankton and fish.
The blue and green algae, will form a layer on top of the water which cuts off light, compared to the diatom algae, which are free-floating and sink to the bottom, where they are eaten by zooplankton. The fish then feed on the zooplankton and the natural pond cycle is balanced.
Cyanobacteria (Blue-Green Algae): Cyanobacteria is actually a bacteria, rather than an algae and has a similar appearance. It may strongly manifest itself during algal blooms when the temperature increases. You can filter out excess nutrients in the water to help slow down growth naturally by introducing certain pond plants.
If left untreated, this algae will form a blanket of slime over the entire pond. This reduces effectiveness of healthy algae, which needs sunlight, as part of its photosynthesis process for growth. Blue green algae can be a toxic risk and danger to pets.
String Algae (Filamentous): This species of algae can attach itself to rocks, waterfalls and even plants, making a not very attractive pond. It is stringy, hairlike, and incredibly fast growing with ability to double its weight within 24 hours.
However, filamentous string / hair algae does not pose the same dangers as Blue-Green Algae, though it may reduce the oxygen level in the pond as it consumes oxygen during its photosynthesis process. Most want to remove string algae because of the way it looks.
Various types of algae eating fish will naturally consume string algae as a food source year-round. For instance, Koi will eat string algae if they are fed less, as well as during winter hibernation months and becomes more scarce.
It is important not to overfeed fish, as leftovers in the pond will greatly contribute to algae growth and with koi they will not be as hungry to eat your algae. Excess nutrients from uneaten food and fish waste, convert into nitrates and ammonia, which can also be harmful to fish in large amounts.
The best algae eating fish for a pond are Koi, Channel Catfish, Chinese High-Fin Banded Shark, Flying Fox, Pond Loach, and the Japanese Trapdoor Snail. After our interviews, research, and trial and error, we recommend the following inhabitants to help you manage algae in your pond the natural way!
PRO TIP: Combine these algae eating fish with healthy diatom algae to help oxygenate your pond, feed your fish, and restore algae ridden ponds back to clear water. Diatoms stifle the growth of bad algae by taking the nutrients needed for their growth, and using it for their photosynthesis process, killing out the bad algae.
Each of the following fish have descriptions on minimum pond size, average fish size, life expectancy, water conditions, pond type and other helpful information to help you choose which is best for your pond.
Generally the most popular fish to add to your pond, Koi come in over 100 different varieties, that can be breathtaking to look watch. A koi fish’s ability to help eat algae often is overlooked as a benefit.
If you want to get your koi to help more, try developing a hand-feeding relationship with your koi, and then try hand-feeding them algae from your pond. It doesn’t always work, but we have seen some koi develop a taste for algae with this method.
There is a fish that snacks more heavily on algae though it may not be as social. What fish is that? The very next on our list.
Over 1,000 Gallons
12 to 15 inches
25 – 35 years w/ sexual maturity at 2 to 3
A pond with at least 1,000 gallons is recommended. Plan for a larger pond than originally needed so you can expand.
Koi prefer water temperatures between 61˚F – 72˚F (16.0˚C- 22.0˚C) with a pH level between 6.9 – 7.8.
Generally docile but may show signs of aggression during mating season.
Channel Catfish are known for their catlike appearance due to whisker like tendrils. It is an amazing algae eater as an omnivore and scavenger. It is really quite the famous fish and are bottom feeders.. You’ve probably seen them during fishing trips and pond shop visits, especially true if living in North America, as they are in abundant supply within the region.
Catfish can be aggressive. They may attack and eat other fish of their size or crustaceans, which can be dangerous depending on what fish already exist in your pond. However, they can also be good pond mates depending on environment and food available. Catfish will also snack heavily on different algae, but could also eat your expensive koi food and bully out your koi.
If you are looking for a fish that tends to be a bit more social, while also eating algae, our next fish may be for you!
Over 1,000 Gallons
15 to 24 inches
15-20 years
A pond with at least 1,000 gallons is recommended. At least 8 ft deep with edges of pond sloping quickly to 3 ft deep, which reduce aquatic vegetation problems.
Channel Catfish prefer water temperatures between 75.2°F-86°F (24oC–30 oC) with a pH level 5.5-7.5.
Channel Catfish can be aggressive toward other fish and eat a variety of both plant and animal matter.
On top of it’s algae eating diet, it is cool to say that you own a shark! The Chinese Hi Fin Banded Shark is actually part of the Catostomidae family in a group of fish known as suckers.
These fish are not “suckers” when it comes to sucking up algae. Most of its diet can consistent of only natural algae! They tend to do well in groups, so you may wish to consider introducing a few at a time in the pond.
With their trademark high fin reminiscent of a shark combined with their docile nature, they can be pretty fun to watch swimming through the pond.
The Chinese Hi Fin Banded Shark is definitely a friendly fish and can socialize well with others. This is another big plus, as not all fish get along well with others, even though they may be great algae eaters.
What fish fits this description? The one just below.
Over 1,000 Gallons
Up to 39 inches
25 years, reaching sexual maturity around 5 or 6.
Use a pond or water garden with 1000 gallons or more of well-filtered, moving, and well-oxygenated water.
Temperatures between 61˚F – 72˚F (16.0˚C- 22.0˚C) with a pH level between 6.9 – 7.8 work well for this fish. Can tolerate temperatures as low as 40˚ Fahrenheit.
Peaceful/Docile. Offer krill, earthworms, and prepared fish foods like koi pellets to keep the bottom feeder coming to the top for meal time.
The Flying Fox, originating from Southwest Asia, is notorious for eating green algae. You can find this small fish zipping to and fro, nibbling down on algae growing on rocks, plants, waterfalls, and elsewhere it can graze. This fish can stress other fish with its energy and may require more oxygen than others.
Yes, some algae eaters will nibble down plants. Finding a balance between algae eating fish and pond plants that remove excess nutrients will help your pond glisten in natural clear beauty!
The Flying Fox appearance is quite nice, and actually somewhat similar to another great algae eater, the Pond Loach!
Minimum 30 gallons
Up to 6 inches
8 to 10 years
Minimum 20 gallons. Keep your Flying Fox in groups with larger numbers, to see how peaceful they can be. Plan for a larger pond to accommodate plants where it can rest and have multiple Flying Fox.
Flying Fox prefer water temperatures between 75°F – 79°F, (24 – 26 C); with a pH level between 6.0-7.5
Typically docile, may become territorial at times. Well-manners with other species, but has been found to chase its own species.
We mentioned Koi being one of our favorite fish and the importance of pairings when introducing different species of fish into a pond. You’ll find the Pond Loach can be a great match!
Its always good to quarantine new fish before introducing them to the main pond to be sure they are healthy and free of disease. These are very hardy fish and can live in poor water quality.
Having a couple Koi and Pond Loach could be a great way to combat algae in your pond. Beyond being bottom feeders, Pond Loach are known to snack on insects and small aquatic critters.
The loaches are active fish that will hide and explore. You may find that it will disappear after introduction to your pond and reappear later. They have a strong jumping ability, so add barriers and look in filters if your pond loach is not coming out to play.
Minimum 20 gallons
Up to 12 inches
7 to 10+ years
At least 55 gallons
Pond Loach prefer water temperatures between (68-72°F, 20-23°C) and can do well even at temperatures as low as the upper 50’s Fahrenheit (13-15° Celsius) with a pH level of 6.5-8.0.
Typically docile and hiding but can be active yet peaceful. May become territorial at times. Does great with koi and goldfish.
Probably one of the most docile algae eaters on our list, is the Japanese Trapdoor Snail / Chinese Mystery Snail! Trapdoor snails can pick up loose food, as well as eat soft algae, for those times where we may have overfed our fish and have some leftovers on the pond floor.
They will also eat algae off stems of plants, but not the plant, making them a good fit for water gardens. Ensure there is enough naturally occurring soft algae for them to eat.
Snails can be a lot of fun to have, but be warned… they also can cause pollution to a pond in the form of waste, which may be worse than the algae they consume. For pond owners with a lot of Koi fish, other pairings may be a better fit.
Any sized ponds.
About 1 to 3 inches
1 to 5 years
They can be kept in small ponds and larger sizes but keep in mind they will add to tank waste so avoid overstocking. Japanese Trapdoor Snails are very active in low light settings.
Japanese Trapdoor Snails are one of a few snail varieties that can over-winter well 7 survive in harsher northern climates. 64 to 84 °F (12.8-28.9 °C)
They only breed a few times a year and will not take over your pond how other nuisance egg bearing snails will.
PRO TIP: It is important to not overfeed. Reducing feed will force your fish to eat more algae, and more importantly, further prevent the growth of algae! Leftover uneaten food creates excess nutrients in the pond, which can fuel algae growth and be harmful to fish.
Every pond is different and you must evaluate your current inhabitants to decide which will play nice together. Certain fish will grow too big for your pond and others will do best when you group them together. Learn our recommendations for why you may or may not want to select each of these algae eaters.
Koi fish do not have a diet centered around algae, but they will consume it if they are hungry, especially during the winter hibernation, when food is scarce. Occasionally a koi can eat smaller fish too!
The Chinese High-Fin Banded Shark to consume algae well, but it is also a larger fish, and could require a larger pond to really thrive.
The Siamese Flying Fox is a great algae eater and can go well in groups, but needs a well oxygenated pond to simulate the oxygen rich ponds from its origins. This fish can also be too energetic with other fish and add extra stress to fish that tend to be more calm.
The Pond Loach is recommended for new pond owners. It is durable and will consume a lot of algae, while not requiring too much maintenance.
The Japanese Trapdoor Snail is a very docile algae eater who can act as a waste manager scouring the pond floor for leftover food and other edible material. Adding in snails will help support your other pond fish and create your full-time clean up crew!
Channel Catfish will not only eat algae, but dead or decomposing fish. It can be aggressive with other fish, so be careful to do your research before adding to pond.
Pleco fish we DO NOT recommend the pleco fish since it will eventually grow too large for your pond and take too much of the available oxygen.
You can create a healthy food chain, with crystal clear water, the natural way!
Diatoms, bacteria, and zooplankton will work together as nature’s filter to consume the extra waste in your pond.
We do not recommend you use copper algaecides, UV lights, and other quick-fix band aids. When you are consistently damaging the pond’s ecosystem, you will never allow your pond to thrive how it would with a natural cycle.
You need to increase the dissolved oxygen (DO) in your pond to control algae. If you are not able to improve the diffusion of oxygen into the water, than you are working against the natural cycle.
To create a strong anaerobic cycle, you need strong bacteria paired with essential nutrients to encourage diatom growth, which photosynthesize and increase the amount of DO in your pond’s water column. If you play by the rules nature intended, you’ll be rewarded in the long-run rather than constantly battling the algae to remove it completely. Algae is your friend, your fish’s diet, and the greatest oxygen creating tool available for your pond.
When you create diatoms (good algae), to be consumed by zooplankton, which are consumed by fish, and improving the natural water cycle, you will remove waste and help sustain life.
Nualgi Ponds has been designed to grow diatoms, create more oxygen, and customers find it to be the best solution for removing algae, while also creating a stable environment for all inhabitants. Click “Try Nualgi” to learn more below.
Did you find this article helpful? Drop us a comment below or if you have any pond specific questions, our pond experts are always available to help troubleshoot.
