One of the most common problems in freshwater aquariums is an overabundance of algae. Some algae growth is normal, but if left unchecked, these photosynthetic organisms can quickly take over your tank. Adding the best algae eaters to your aquatic community can help keep your aquarium clean the easy way!
A GUIDE TO FRESHWATER ALGAE EATERS
Algae is a common problem in both new and mature aquariums. It’s completely normal to have to scrape algae growth off the sides of a tank, but it can be more of a hassle to clean substrate, equipment, live plants, and décor. Algae-eating invertebrates and fish tank cleaners can help alleviate the problem!
WHAT ARE ALGAE EATERS?
Algae eaters include a wide variety of fish, shrimp, and snails that feed entirely or primarily on algae and other plant material in an aquarium. Depending on the species, algae eaters can eat a wide swath or target a specific variety of algae. These aquatic organisms are a great choice for community tanks of all sizes!
HOW EFFECTIVE ARE ALGAE EATING FISH AND INVERTEBRATES?
The effectiveness of your algae feeders will depend on:
- Your aquarium, filtration and lighting setups.
- The types of algae and live plants in your tank.
- The type and number of algae eaters in your community aquarium.
Some species like Siamese Algae Eaters, American Flag Fish, and amano shrimp are champion algae eaters and can make a significant dent in a troublesome tank. Others, such as Plecostomus and its fellow catfish, act as scavengers, cleaning up food debris in addition to eating algae.
It’s often a good idea to have a couple of types of algae eaters in your community. Consider getting a variety that is an algae eating machine and then fill in the gaps with some scavengers and species that munch on decaying plant materials. This will allow you to strike a balance in your algae battles and help keep your tank cleaner.
HOW TO CHOOSE AN ALGAE EATER FOR YOUR TANK
The best way to choose an algae eater for your tank is to find one that suits your current community. Choose a species or two that are compatible with the other fish and invertebrates you have and that work with the size, temperature, pH, and hardness of your aquarium water.
Most algae eaters prefer densely planted tanks, although some species do well in tanks without live plants. However, your type of substrate is important. Many algae eaters live on the bottom and prefer soft substrates such as sand and fine gravel to pea-sized aquarium gravels that cause injury.
ALGAE EATERS FOR NEW AQUARIUMS VERSUS MATURE TANKS
It’s usually a good idea to wait a few weeks before adding an algae eater to a new tank to give the filter time to cycle. While algae often bloom during the «new tank syndrome» stage, it’s not a good idea to add an algae eater until things have settled down and there’s a consistent, abundant food source for them.
Avoid adding species that feed on biofilms to a new or recently recycled tank. It takes a few months to develop a healthy matrix in a new tank and they will starve in the meantime. These species are best kept in mature aquariums with a healthy, balanced mix of biofilm and algae. Next, I cover more about biofilms.
If your tank frequently has problems with a specific type of algae, then you can choose an algae eater that likes to nibble on that type. This is a slow and gradual process and it may take a few weeks to see a substantial difference. However, not all types of algae are edible, so you may need to take other steps as well.
TYPES OF FRESHWATER ALGAE
Algae is the general term for aquatic organisms that convert the sun’s energy into food through photosynthesis. Algae can be single-celled or multicellular organisms (seaweeds are a type of algae) or can grow as a biofilm in a protein matrix with bacteria and fungi. The types of algae you are most likely to see in your tank include:
HAIR OR THREAD ALGAE
Hair or thread algae are a filamentous species that form soft green threads on living plants, decorations and on the surface of their substrate. It’s called hairweed because it’s long and feels like wet hair when you pull it off. It is a type of algae that grows very fast and is not easy to eradicate.
Causes
Hair algae is often a problem in a tank that has too many nutrients built up in the water. Excessive light shining into the tank or high iron levels can also cause hair algae to appear. By the time the issue is resolved, CO2 and nitrate levels have also plummeted.
Options to solve a problem of algae in the hair
In addition to correcting your water chemistry and adjusting your lights, you might consider adding Amano Shrimp, Fancy Mollies, Siamese Algae Eaters, Mystery Apple Snails, or American Flagfish to your tank to help consume problem weeds.
BROWN SEAWEED
There are two types of brown algae, but one type, brown slime algae, only grows in saltwater environments. The brown algae that grows in a freshwater tank is a type of diatom that can photosynthesize and convert energy from the silica, phosphorus, and nitrates in your tank.
Brown algae begin as a layer of yellowish-brown or reddish-brown specks on glass, substrate, live plants, and décor. The «powder» feels a bit gritty when you rub it between your thumb and finger. Within a week, the dust turns into a layer of brown slime that coats the entire tank.
Causes
Most of the time, a brown algae bloom means you have too many nutrients in your tank along with low oxygen levels and inadequate lighting. If you fix these problems, the algae may go away on its own. It may take a couple of months to clear up naturally.
Options for dealing with brown algae
It is very common to have problems with brown algae in a new aquarium, but these are usually resolved once the tank has cycled through. If you develop brown algae in a mature tank, you probably have a water quality problem. There are fish that eat brown algae, so add Catfish or Plecostomus otocinclus to your tank to help prevent outbreaks.
BLACK BEARD ALGAE (BBA)
Despite the name, blackbeard algae or BBA is actually a type of red algae in the Rhodophyta family. It forms clumps of slippery black or purplish threads on any of the hard surfaces in its tank and resembles a ragged beard. This algae is an aquarist’s nightmare with mature tanks! It is also incredibly difficult to remove.
This material grows on glass, the leaves of your plants, on swamp and driftwood decorations, and on your gear. It’s not hard to scratch your glass, but good luck with your plants and decor. I have pruned the plants instead of trying to remove a heavy load of BBA. The only good thing is that it tends to be slow growing, so it doesn’t spread quickly.
Causes
The most common reason for a BBA bloom is inconsistent lighting or a combination of factors including inadequate circulation and low or unstable CO2 levels. You will often see BBA in mature tanks on slow growing plants where it is easily pruned. If you see a sudden spike in BBA, you should try to identify the problem.
Removing Blackbeard Algae From Your Tank
Once you have identified and fixed the problem that caused the algae bloom, you need to mechanically remove as much BBA from your equipment, plants, and décor as possible. Then control further outbreaks by adding Siamese Algae Eaters, Amano Shrimp, or American Flagfish to your tank.
GREEN POWDER ALGAE (GDA)
There are many varieties of green algae, and green powder algae or GDA is a term used for various slime-producing species. GDA appears as a layer of green slime on your glass, equipment, live plants, and substrate. Unlike the green spot algae below, GDA does not form in clumps, but instead coats everything in the tank at the same time.
Causes
It is commonly seen in new aquariums that do not yet have an established bacterial base, but occasionally appears in mature tanks as well. If you’ve just added a bunch of plants to your aquarium or are pruning them back, you could see an outbreak of GDA. It often happens when there is an imbalance of CO2 and nutrients.
Cleaning green dust algae from a tank
You can easily clean the green slime off your glass and equipment, but this will actually cause the algae to release spores into the water and perpetuate the bloom. Alternatively, consider waiting for it for a month. That will naturally complete the life cycle of the algae.
Four weeks later, remove as much of the water as possible, then before putting it back in, wipe up as much of the slime as you can with a rag. Don’t let the mucus fall into the water still in your tank. Then refill your aquarium and add a Bristlenose Plecostomus to chow down on the rest!
GREEN SPOT ALGAE (GSA)
Green spot algae (Coleochaete orbicularis) or GSA is another species of green algae. GSA starts out as small, hard green dots on your aquarium glass, equipment, slow-growing plants, and decor. If the conditions in your tank are right, the dots will begin to expand until your tank is covered in algae.
Causes
GSA is often seen in recently cycled tanks, but usually only becomes a problem when there is a nutrient imbalance, too much light, or insufficient CO2 for live plants. GSA sticks firmly to your glass and decor and can be a challenge to scrape off.
Fix a Green Spot Algae Outbreak
In new tanks, you can often wait for the problem to go away and remove the algae once the tank has finished cycling. For a mature tank sprout, you should check your phosphate levels and correct them with a phosphorus supplement if they are out of balance. Then clean the GSA and see if it happens again.
If that doesn’t fix the problem, try adding more CO2 to your tank and dimming your aquarium lights.Nerite snails can also help keep it in check because they are great at scraping GSA off glass, plants, and decorations.
GREEN WATER ALGAE
Have you ever had an algae bloom that turned your tank water into something akin to pea soup? Then you will be familiar with an outbreak of green water algae. This unicellular algae from the Euglena family is hard to fight because it replicates so fast! You can do a massive water change and be back to soup in 24 hours.
Green water algae will not harm your fish, but it will reduce the amount of light your plants receive. Also, you will not be able to enjoy looking at your aquarium. This is an especially common problem in new tanks that are in operation and recently planted tanks.
Causes
Green water algal blooms are usually triggered by an increase in light and nutrients in your tank. Maybe the sunlight is hitting your tank or you are overfeeding or you just added fertilizer for the plants. If plants don’t use all of these extra nutrients, they can build up and algae floating in the water go into a feeding frenzy.
Tackling the Green Water Algae Bloom
It can be a real pain to deal with a tank that has a green water algae outbreak because you can’t fix the problem simply by stabilizing the water chemistry. Algae reproduce too quickly for water changes to have much of an effect.
It is best to prevent green water algae blooms by using a light timer and blocking sunlight from your aquarium. If you keep up with the water changes and filter maintenance, hopefully you won’t have ammonia spikes. Adding snails and shrimp to the tank can consume the algae early on before the soup forms.
Consider adding a UV sterilizer
If you can’t get things under control by fixing the excess light and nutrient problem, then you’ll have to resort to killing the algae. You can do this by completely shutting down your tank for a few days, similar to treating blue-green algae. Of course, this could also kill your live plants.
A better option is to purchase a UV sterilizer or invest in a high-quality filtration system that includes a UV disinfection stage. Running your aquarium water through a filter like this will kill algae cells and quickly clean the water. These devices also work very well to kill microorganisms that could harm your fish or invertebrates!
BLUE-GREEN ALGAE (BGA)
The last type of algae you often see in freshwater tanks is an oddball. Blue-green algae or BGA are not true algae, but rather a type of photosynthesizing, nitrogen-fixing microorganism called cyanobacteria. It forms a thick layer of blue-green algae on glass, substrate and equipment.
You will usually see the heaviest buildup in the parts of your tank that receive the most light, such as the front of the tank or the part closest to a window. BGA feeds on the organic waste products in your tank and is a sign of poor water quality.
Causes
BGA usually occurs in overfed tanks with infrequent water changes and too much light. Unbalanced water chemistry causes algal blooms and the BGA quickly takes over. It is difficult to eradicate because it grows very fast and duplicates itself in just 20 minutes.
How to get rid of blue-green algae
The first thing to do is test your aquarium water and correct the water chemistry. Remove as much of the BGA from your tank as possible. You can even lift or vacuum it out of your substrate. Adding more fast-growing plants like hornwort can help because they will compete with the BGA for nutrients.
Next, evaluate your aquarium lights and filtration. If BGA is forming in parts of your tank without proper water circulation, consider adding another filter to improve things. A good 3-stage filter and reduced lighting may be enough to reverse the outbreak.
If that doesn’t work, your final options are to completely shut down your aquarium for a week to «starve» the BGA, or to dose your tank with antibiotics like Maracyn. Unfortunately, there are no algae eaters that consume BGA, so we have no way to naturally control an outbreak.
| Type of algae (family) | Appearance | Causes | Solutions | algae eaters |
| Hair / Thread (Filamentous) |
Long, fine green threads in live aquarium plants and substrates | Unbalanced nutrients and/or too much iron Low CO2 and/or nitrate levels Too much light | Test and improve nutrient balance Increase CO2 Reduce light levels | Amano Shrimp Deluxe Mollies Siamese Algae Eaters American Flag Fish Mysterious Snail |
| brown (diatom) | Dust or spots of brown algae that spread quickly in a slimy mat that covers the entire tank. | Inadequate lightingPoor water qualityLow oxygen levels | Mechanical removal Add or increase filtration Increase frequency and number of water changes Improved tank lighting Increase water oxygenation | Plecostomus otocinclus catfish |
| Blackbeard (Rhodophyta) | Bunches of brown, black, or purple «hair» that look like bread growing on glass, equipment, live plants, or décor | Low or unstable CO2 levels Inconsistent light levels Poor water circulation | Mechanical removal where possible Increase CO2 levels Improve filtration and circulation Adjust lighting conditions | Siamese Algae Eater Shrimp Amano America Flag Fish |
| green powder | A thin layer of green slime that coats glass, equipment, live plants, and substrate. | The New Tank Syndrome Nutrient and CO2 Imbalance | Wait 4 weeks, then clean the tank. | Bristlenose Plecostomus |
| Green Spot (Coleochaete) | Small, hard green stains on glass, equipment, live plants, and décor. | Nutrient imbalance or low phosphorus levels Low CO2 Too much light | Check/adjust phosphate levels Increase CO2 Reduce light | nerite snails |
| Green water (Euglena) | Free-floating microscopic algae bloom fills your tank with densely green water | New tank syndrome A sudden increase in light (sunlight) Increased nutrients from overfeeding or poor maintenance | Wait for tank to finish cycling Lower or remove aquarium light Correct nutrient balance Add UV sterilizer to tank | shrimp snails |
| Blue-green (cyanobacteria) | Slimy mat of blue, green, brown, or reddish-purple algae spreading across the substrate and front of the aquarium | Poor water qualityPoor filtration and circulationInfrequent water changesToo much light | Increase frequency and amounts of water change. Improve filtration and circulation. Reduce or eliminate light in tank (blackout) Use antibiotics to kill bacterial infection. | none known |
TIPS FOR ALGAE CONTROL
You may have noticed a few themes when I described the causes and solutions to algal blooms in our home aquariums. While an algae bloom may be something to expect as your new tank cycles, in mature tanks they are usually a sign of a larger problem.To prevent algae blooms in your freshwater tank:
- Add a variety of algae eaters to your community to naturally clean your aquarium.
- Keep up with water changes and routine maintenance.
- Don’t overcrowd your tank with fish, snails, and invertebrates.
- Don’t overfeed your fish or let the excess food in their tank go bad.
- Use the correct number of 3-stage filters for your tank size and replace filter pads and media on a regular basis.
- Limit the amount of natural sunlight that reaches your tank and keep aquarium lights on a timer. Most tanks don’t need more than 9 hours of light a day, so reduce your hours if you have algae problems.
- UV sterilizers can kill free-floating algae cells and prevent some outbreaks.
21 BEST FRESHWATER ALGAE EATERS
Let’s take a look at some of the best and most popular algae eating fish, snails and shrimp for freshwater aquariums. One thing to keep in mind is that most algae consumers are very sensitive to water quality. If you have detectable levels of ammonia in your tank, they will suffer. You’ll need to keep your tank clean for them to keep working!
Invertebrate algae eaters are often very sensitive to copper-containing plant fertilizers and aquatic medications. Make sure the products you use in your tank are safe for your new pets!
1. SIAMESE SEAWEED EATER
An excellent choice for tanks larger than 20 gallons, the Siamese Algae Eater or SAE is an eating machine. Although these omnivorous fish prefer live foods, they are some of the few that consume black hair and beard algae. Not to be confused with the nearly identical Flying Fox fish, the SAE is an excellent choice for algae control.
These social and energetic fish enjoy hanging out together and feeding on algae and leftover food. They are not aggressive but their activity can be distressing to bottom feeders and other territorial fish, so they are not a good fit for cichlid tanks. They can also get nimble around long fins, so avoid sticking with angelfish and discus.
| Common name (species) | Siamese algae eater, SAE (Crossocheilus siamensis) |
| Family | Cyprinids |
| Temper | Peaceful, active and social |
| level of care | Easy |
| Diet | Omnivore; prefers live foods but will eat algae. One of the few fish that BBA consumes! |
| Color | Grey/gold body with a black stripe running from the mouth to the tip of the caudal fin |
| Size | 5 to 6 inches long |
| Minimum tank size | 20 gallons |
| Temperature range | 75 to 79°F |
| Hardness of water | 5 to 20KH |
| pH range | 6.5 to 8 |
| Tank Mate Compatibility | Active fish are best kept with other peaceful community fish. It can bite fish with long fins. It is not ideal for cichlid tanks and may disturb territorial bottom feeders due to its activity. |
2. CHINESE SEAWEED EATER
>The strangely named Chinese algae eater is not native to China, but it does have a voracious appetite and preference for eating algae. Unfortunately, this Southeast Asian species also outgrows its love of algae and becomes a bit of a nasty problem child as it matures. These semi-aggressives are not ideal for peaceful tanks.
If you have a large, semi-aggressive community tank over 50 gallons, you may be able to slip a Chinese algae eater inside with no problem. Young fish continually feed on algae and still eat them as they grow. Since they establish and defend their territory, you should only have one fish per tank.
| Common name (species) | Chinese Kelp Eater, Indian Kelp Eater, Sucking Loach ( Gyrinocheilus aymonieri) |
| Family | Gyrinocheilidae |
| Temper | Semi-aggressive and territorial |
| level of care | moderate to difficult |
| Diet | Omnivore; algae when young, insects and larvae, worms |
| Color | Pale brown with black streaks or spots on body; Albino and golden varieties available. |
| Size | 10 to 11 inches long |
| Minimum tank size | 50 gallons |
| Temperature range | 71 to 80°F |
| Hardness of water | 8 to 10KH |
| pH range | 6.0 to 8.0 |
| Tank Mate Compatibility | It is best kept alone or with smaller, fast-swimming fish such as Tiger Barbs that avoid the bottom and middle of the tank. Not ideal for peaceful community tanks. Avoid housing with discus, invertebrates, or other Chinese or Siamese algae eaters. |
3. TWIMMING CATFISH
If you have a large, densely planted mature tank over 40 gallons, you might consider adding one of the more unique looking algae eaters on the list: the Twig Catfish. These funny looking fish resemble a branch or stick and are masters of disguise. They love to cling to plants or the swamp in your tank as they feed.
These shy algae eaters are ideal for peaceful community tanks and are happy to be with their own kind and other friendly species. They are extremely sensitive to changes in water quality, which makes them a bit difficult to maintain. But they do add an interesting element to your tank and do a great job of keeping algae in check.
| Common name (species) | Twig Catfish (mainly Farlowella vittata or acus) |
| Family | Loricariidae |
| Temper | peaceful and shy |
| level of care | moderate to difficult |
| Diet | Omnivore but mostly vegetarian; eat biofilms, algae and blanched vegetables. Occasional treats of brine shrimp, bloodworms, or Daphnia eggs are readily accepted |
| Color | Light brown with darker brown lines or spots |
| Size | Grows up to 6 inches long |
| Minimum tank size | 40 gallons |
| Temperature range | 75 to 79°F |
| Hardness of water | Soft to hard as long as it’s consistent |
| pH range | 6.0 to 7.0 |
| Tank Mate Compatibility | Best kept with other branch catfish or in community tanks with small, friendly fish like Cory Cats, Neon or Rummy Nose Tetras, or Pearl Danios |
4. CATFISH otocinclus
>If you’re looking for tiny algae eaters or options to control brown algae blooms, consider Otocinclus catfish, commonly known as Otto. Ottos only grow to a maximum of 2 inches in length, making them a suitable choice for most tanks. These peaceful fish enjoy school and schools between meals.
Like many catfish, the Otto is a scavenger, but unlike most it is also a herbivore, feeding entirely on algae and decaying plant material. A group of these algae-eating monsters can prevent outbreaks or blooms, and they work with most peaceful community groups.They are one of the best options for algae control!
| Common name (species) | Otocinclus, Ottos, Dwarf Sucker Catfish, Dwarf Sucker Catfish (Otocinclus vestitus) |
| Family | Loricariidae |
| Temper | Pacific school of fish |
| level of care | Easy |
| Diet | Herbivorous; decomposing algae and plant material |
| Color | Mottled gray body with black spots |
| Size | 1 to 2 inches long |
| Minimum tank size | 10 gallons |
| Temperature range | 72 to 82°F |
| Hardness of water | 6 to 15KH |
| pH range | 6 to 7.5 |
| Tank Mate Compatibility | Best kept in a school along with other small, peaceful community fish such as tetras, rasboras, and loaches. |
5. WHIPTAIL CATFISH
If you thought the Twig Catfish looked interesting but too difficult to maintain, check out the similar looking Whiptail Catfish! Whiptail cats are closely related to Twigs, but are smaller and much easier to care for. Unfortunately, the Whiptail is also an omnivore and prefers to eat other things besides the algae in its aquarium.
Whiptail cats will eat the algae in your tank, but prefer to eat algae wafers and food scraps. You may need to encourage them to pick at the algae if you have a problem, but between blooms you should supplement their diet with sinking catfish pellets and wafers. These fish are also a lot of fun to watch!
| Common name (species) | Whiptail catfish (multiple species of Rineloricaria) |
| Family | Loricariidae |
| Temper | Calm |
| level of care | Easy |
| Diet | Omnivore; prefers a carnivorous diet of catfish pellets and algae wafers to eating tank algae |
| Color | Pale to dark brown with streaks or specks of darker colors |
| Size | Varies by species, but generally 3 to 6 inches long. |
| Minimum tank size | 20 gallons |
| Temperature range | 72 to 79°F |
| Hardness of water | 3 to 15KH |
| pH range | 6.0 to 7.5 |
| Tank Mate Compatibility | Best kept with a few other whips or in a peaceful community tank with no aggressive or agile species. |
6. BRISTLENOSE PLECOSTOMUS
One of the best options for eating algae in a 25+ gallon tank is the fascinating Bristlenose Plecostomus. More popular than the larger, semi-aggressive Common Pleco, the Bristlenose develops long tentacles around its
