Freshwater Fish

Do Mollies Eat Algae? And Is It Really Useful And Helpful?

Are you having an algae outbreak in your fish tank? Are you constantly cleaning your aquarium because of those annoying green jelly-like blobs that either float or cover that decorative stuff, plants, and walls of your aquarium?

Most aquarium hobbyists will agree that having algae inside the aquarium diminishes a fish tank’s aesthetic look or attractiveness.

Aside from making your aquarium looks dirty and cloudy, cleaning takes a lot of time and effort. That is why algae outbreak is one of the most common concerns of aquarium enthusiasts.

Well, here’s good news for you! If you haven’t heard about it yet, did you know that mollies can help you control algae? 

You’re probably wondering, do mollies eat algae? The truth is, they actually do! Let’s delve deeper into the topic.

What Are Algae?

A fourth-grader student will probably define algae as an organism from the kingdom of Protista. Apart from being a staple food of many fish and aquatic creatures, it’s also a source of nutrients in the oceans.

It’s one heck of a microorganism! But for aquarium enthusiasts like us, they’re villains, and villains must be eliminated. 

The menacingly excessive growth of algae makes the aquarium look dirty and unattractive. However, algae thrive in every aquatic ecosystem.

It is nearly impossible not to have algae in every fish tank. But the good thing is, the growth of algae can be minimized up to a tolerable level.

There are a number of things that you need to know first before you can fight algae. One of these is finding the roots cause. Why do algae grow in your aquarium?

Algae thrive where there’s an imbalance of nutrients and light in the aquarium ecosystem. If your aquarium is low in nutrients but is exposed to too much light, algae will use the excess light to reproduce.

On the contrary, if you lessen the light and provide many nutrients, algae will take advantage of excess nutrients to grow.

So, the solution could be to balance light and nutrients in the water. 

Unfortunately, balancing nutrients and light is nearly impossible because your aquarium plants continue to grow, use, and dispose of nutrients.

Additionally, it can be challenging to add chemicals.

Although there are ones good for aquariums, its mind still ends up harming your fish. You would also need to do it frequently to avoid algae in your tank.

Moreover, it can take up too much time. Balancing the ecosystem would still be the best option. It’s also the most cost-effective.

Can Algae Kill A Fish? 

In a natural setting, algae are beneficial to the balance of the ecosystem because most aquatic animals eat algae. However, too many algae can deplete oxygen in the water.

When the water has not had enough level of oxygen, fishes and other aquatic animals will end up competing for it. 

So instead of helping, you might end up killing them. It can happen to all small bodies of water, such as ponds, small lakes, and swamps.

This can also occur in your aquarium. If not adequately controlled, excessive algae endanger the fish in the fish tank.

So, how do we solve the problem of algae? We have learned that it is nearly impossible to create a balance, but we can always minimize the imbalance.

Just by regularly monitoring the amount of light in your aquarium, you can reduce the growth of algae. 

To fill the gap, you need to get an algae-buster crew. This is where mollies fit in. Basically, they are known in the aquarist circle as good algae busters. 

They come in different varieties and colors to choose from. These are the lyretails, dalmatians, sailfins, gold dust, gold doubloon, balloon belly, and the all-time favorite black. 

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What Are Mollies?

A molly is a species of fish that comes from a vast family of fish. According to Encyclopedia Britannica, molly comes from a variety of tropical fish of the genus Poecilia.

It belongs to the livebearer family, Poeciliidae, and it can grow from 5 up to 13 cm (2 to 5 inches) long. 

What’s impressive about this fish species is that it’s a livebearer, and there’s also the fact that it can rapidly reproduce.

Most varieties thrive in any kind of aquarium, and they can even live in a wide range of environments, even in hard water.

However, there are a few types that require you to add a small amount of salt to the tap water. Since they are a small breed of fish, you only need 30 gallons of water for their living space.

Depending on the variety, a molly can grow anywhere from 3 inches to 6 inches. 

This species of fish is highly recommended for beginners since it’s quite easy to care for. Also, some molly varieties have unique shapes and colors which can add vibrance to your fish tank.

Mollies can tolerate a wide range of environments; therefore, it is suitable for any aquariums. Besides, they’re easy to maintain and can even help clean out your tank. 

Do Mollies Eat Algae

Types Of Molly Fish

That said, here are the most popular types of Molly fish species you can choose from:

Lyretail Mollies

Lyretail Molly (Poecilia latipinna)

Lyretails have lyre shape tails, hence the name. They come in different varieties, but they have common needs and characteristics.

This type of molly is generally peaceful, with a 7.0 to 7.8 water pH requirement and only around 68-82 degrees Fahrenheit temperature requirement.

Platinum Lyretail Molly

This variety comes with a silvery color scale. It can grow up to five inches and can live in both saltwater and freshwater aquariums. To make a freshwater aquarium suitable for living, you’ll have to mix in one teaspoon of salt per gallon.

Marble Lyretail Molly

As the name suggests, this molly variety features a combination of black and white scales. Aside from that, its design resembles a marble.

Black Lyretail Molly

This is a hybrid variation of the Sailfin Molly with black scales with a white highlight. A black molly tends to be the most famous variety among mollies when it comes to algae eating.

Dalmatian Lyretail Mollies

Dalmatian Lyretail Molly

True to its name, this molly is covered with black spots over their white scales. It can grow to a maximum size of 3 inches. 

Sailfin Mollies

Sailfin Molly (Poecilia velifera) in Aqaurium

The distinguishing mark of a Sailfin molly is its long tail. Just like the lyre variety, this breed is also peaceful, and they prefer water with a pH of 7.0 -8.0 with a temperature of 68-82 degrees Fahrenheit.

White/Silver Sailfin Molly

white sailfin molly fish

This variety of molly has silvery scales and beautiful long fins. A female silver sailfin molly grows more prominent and heavier than males.

Black Sailfin Molly

This variety of molly is all black and features beautiful flowing long fins. A black molly sailfin holds the status as the most helpful molly in dealing with an algae-infested aquarium.

Golden Sailfin Molly

The golden sailfin molly thrives in a community aquarium with hard water. It grows larger than the average size molly, which makes it best suited to an aquarium with bigger space.

It also prefers aquariums with plants as it can eat soft algae that grow on these plants.

Harlequin Sailfin Molly

This variety has the exact needs of the Golden Sailfin Molly, except for its color. It possesses a dazzling color of gold, white, and black patches.

Creamsicle Sailfin 

It got its funny name from its scale color. The Creamsicle Sailfin Molly is white at the bottom and gold on top. This breed is not sensitive to water temperature, making it great for beginners.

Dalmatian Molly

It has the same scale color as the Dalmatian Lyre Molly. They only differ in the tail. This variety is bigger than the Dalmatian Lyre Molly as they grow to a maximum size of 4 ½ inches.

Balloon Belly Molly

balloon molly fish

It is called balloon belly molly because of its trademark swelling belly. They are friendly fish that like the company of other fishes their size. It grows to about 3 inches.

Black Molly

This breed has beautiful black scales with spots of a different color. Like Balloon Belly Molly, it is a peaceful kind. It lives well with other fishes in the tank.

Gold Dust Molly

Gold Dust Molly

Gold Dust Molly and Black Molly have striking similarities except for the rich golden color of Gold Dust Molly. Most people choose this breed because it adds attractiveness to their aquarium.

Gold Doubloon Molly

Gold Doubloon Molly stands out among the rest because of its bright yellow and black color scheme. Although it has short fins, it can grow up to five inches.

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What Kills Algae In The Fish Tank?

You might be asking which type of molly can clear out algae in the fish tank. Actually, all of them eat algae, but the most effective is the black varieties.

What makes mollies a good algae buster is that most of them are omnivores. They feed on plant matter, plants, and algae. They eat algae on rocks, on aquarium walls, in plants, and on the water surface in the aquarium. 

In most cases, they prefer algae over fish food as part of their diet. Now, you’ve finally found a solution to your algae-infested fish tank but hold it right there.

Don’t get too excited, as there are a few more things to know before rushing to the pet shop.

what kind of algae do mollies eat

Tank Mates

The question you should be asking next is what type of fish get along with mollies. Are they compatible with my existing fish?

To answer that question, here are some species of fish that will live well with mollies.

These are breeds that have the same temperature and water requirements, temperament, and characteristics.

1. Guppies

Guppy fish Poecilia reticulata

Like mollies, guppies are also livebearers.

They are both omnivorous and enjoy the water with similar parameters. Guppy fish grows to a maximum of 2 inches which is smaller than mollies.

To limit the breeding cycle of guppies, it is recommended to keep more males than females. After all, males have more attractive colors than females.

2. Neon Tetras

neon tetra Jumbo(Paracheirodon innesi)

Neon tetras are one of the most liked fish among fish keepers because of their vibrant colors. It is recommended for beginners because it is easy to care for.

This is a good match for a molly because they are friendly and have simple dietary needs.

3. Swordtail

Swordtail fish (Xiphophorous hellerii)

Here’s another type that doesn’t grow big. However, some variants of swordtail have the tendency to be aggressive, especially males.

Their unique shape makes them an excellent addition to aquariums.

Be wary, though, because they have the tendency to jump out of the tank.

Keep your tank covered if you have a swordtail in the group. 

4. Zebra Danio

Zebra DAnio Fish Long-Finned

Zebra Danio is an excellent addition to community aquariums. They are active varieties of fish, but they love to nip at long-tail fishes. So, make sure that you choose the short-finned mollies as their companions.

5. Endlers

Endlers guppy

These are small colorful fish that are closely related to guppies. They are a good match for mollies because they are also active and love to explore.

6. Platy

Platy fish (Xiphophorus spp.)

Platys are a nice variety of aquarium fishes, and they get along with mainly all fishes of their size in the aquarium. Although they are small, which grow only from 1.5-2 inches, they breed quickly.

So, if you don’t want your fish tank to get crowded, limit the number of males in your aquarium.

  • Otocinclus Catfish
  • Siamese Algae Eater
  • Harlequin Rasbora
  • Angelfish
  • Gouramis
  • Plecos
  • Corydoras
  • Minnows

On the other hand, be careful not to house together Bettas, goldfish, aggressive fishes, and shrimp with mollies. 

Aside from not having a compatible water temperature requirement, there are other reasons why some fish should not be put together with mollies. Bettas and other aggressive fishes attack variants with long fins.

As for goldfishes, mollies are known to bully goldfish, causing injuries. The same with shrimp.

The molly fish loves to make shrimp their lunch. So, if you want your mollies to focus on algae, avoid adding shrimp to your tank.

Are Mollies Good For Algae?

We’ve mentioned that mollies eat algae. However, you probably have a few more questions in mind. Things such as are your fish compatible with mollies?

Are mollies worth the try? Do they really work in controlling algae? Here, we gathered some fish keeper’s experiences with the fish.

Here are what people say about mollies as algae-eater:

Black mollies mostly pick on hair algae that grow on the leaves of the plant. To make mollies an effective algae-eater, you need to severely underfeed them.

For the surface algae, one molly can keep 20 gallons of water clear. They would nibble at every piece of algae that hangs off plants.

Whenever they are put on a fresh tank with algae, they eat first the algae, and when the algae are depleted, they begin to look for fish food.

A pair of black mollies can keep the surface of my aquarium is spotless because they pick at algae all day long.

Moreover, green, silver, black, orange sailfins, dalmatian, and black lyretail mollies —  they are a great cleaning crew.

Before, you would probably need to scrub the aquarium regularly, but with just 6 mollies in a 30-gallon tank, algae can be removed in just 3 days. You probably won’t even notice algae growing in your tank afterward.

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Mollies are the most diligent of all the livebearers. They are most effective in picking out hair algae on leaves and stems. They really do an excellent job of controlling algae.

Among the varieties of mollies, it’s the black variant that has received the most mentioned award from fish tank keepers.

Do Mollies Eat Java Moss

What Algae Do Mollies Eat? 

Since algae come in different types, the next most logical question is what type of algae mollies eat? But first, let us identify the common types of aquarium algae.

Brown Diatom Algae

Newly planted tanks are most often infested by diatom algae, especially with high phosphates and silicates. Diatom is a brownish, dusty, flour-like substance that can be seen covering the aquarium walls and other surfaces.

Black Beard Algae

black beard algae or brush algae

It is usually a bushy clump of black or greyish color. These algae grow on driftwood, aquarium décor, and plants. This is one of the most disliked algae because not many fish eat it. Unfortunately, mollies don’t eat BBA.

Hair Algae

It looks like hair hanging off plants. What is problematic about hair algae is that they rapidly multiply and are not easy to get rid of.

So, to prevent it from reproducing, try to decrease your light and increase fertilization or decrease iron. And for the gap, get mollies. They will surely take care of the rest.

Green Spot Algae

This type of algae is found on aquarium walls. They looked like hard, green spots that are very difficult to scrub off. Use a glass scraper to clean off these algae from the walls of your fish tank.

To control its propagation, try to balance light and phosphate. A good first line of defense to these algae is Nerite snails.

Now, which of these algae mentioned above is present in your fish tank? Identifying the type of algae thriving in your tank would help you in strategizing how to get rid of them.

Moreover, adding different methods can also decrease algae.

Do Mollies Eat Hair Algae?

The good news is you can count on a molly to take care of your hair algae. And because they are naturally algae eaters, you are assured that they are getting a good diet.

It is noted that nutrition-wise, algae and other types of green food are necessary for the excellent health of mollies. Hair algae are no exception; mollies get good nutrition from hair algae.

What Is The Best Fish For Eating Algae? 

As you now know, algae come in different types, and no one kind of fish eats all kinds of algae. But there is one fish that feeds on most varieties of algae. It is called the Siamese Algae Eater.

The Siamese Algae eater eats some algae that other algae eaters ignore.  One example of this is the black beard algae (BBA).

This fish species thrive in no less than a 30-gallon fish tank, prefer a pH between 6.5 and 7.0, and a temperature between 75 degrees and 79 degrees Fahrenheit. This variety is relatively easy to care for as long as they have enough algae to eat.

But that doesn’t mean mollies can’t do the job. As long as they’re not BBA, you can count on them to get take care of your tank.

Are Mollies Really Helpful and Useful? 

Even though a molly is not as good of an algae killer as the Siamese Algae Eater, it can still be a lot of help.

Aside from its beautiful varieties, which can add color and attractiveness to your aquarium, it’s also very helpful and useful in eradicating hair algae, which is one of the most problematic algae in a fish tank.

Even if Mollies are most commonly known as hair algae eaters, they also eat few other types of algae, such as the brown diatom algae.

In addition, Mollies are not high maintenance. Beginners can start with mollies with a high rate of success.


There you have it. The growth of algae is not, after all, difficult to control. Just a few mollies will do the job. 

Going back to our first question, do mollies eat algae? Definitely.

Are they really useful and helpful? Absolutely. By having mollies in the house, you can eliminate annoying algae. If algae growth is not managed correctly, it can be a danger to fishes in the tank.

Although algae produce oxygen, the irony is that excessive algae deplete oxygen in the water as it consumes more oxygen than it creates.

So while other methods such as creating a balance in your tank are helpful, they can be hard to achieve. The best way is to do that and add mollies to reduce as many algae as possible.


Passionate fishkeeper. Nature lover. Creative thinker. Music junkie. Adventurer.

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