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Do Mollies Eat Algae? Is It Harmful To Fish?

do mollies eat algae

If you have been putting hours of care and hard work into maintaining your aquarium clean and free of algae, it is only natural to find natural ways to keep it that way for long. Of course, it is well-known that several fish species are specialized algae-eaters. So, can you count on your Mollies to do the job?

Mollies do eat algae as part of their diet. In fact, they are omnivores that mainly feed on plant matter, algae, and small insects . In an aquarium, they will eat algae off the rocks, on water surface, and on plants. However, they are not among the most efficient algae-eaters.

Mollies have been part of any aquarium at least once, and they are not only beautiful but also easy to care for. Find out how they can help you keep your aquarium’s environment healthy below.

What Do Mollies Eat?

Mollies do eat algae, but only as part of a more complete and elaborate diet. They are generally undemanding, but it is crucial to truly understand these small fish’s requirements to see them thrive and reproduce.

When they are free in nature, Mollies naturally feed on plant matter, plants, and algae. However, the original variety has been bred into many hybrids that the small, bright fish in our aquariums don’t follow the same diet any longer.

Of course, plants and algae still represent an essential aspect of their diets, but they are not the only source of nutrients for Mollies.

Looking After Your Mollies’ Nutrition

white mollie
Mollies are famously undemanding fish that will fit well in the aquariums of beginners or inexperienced aquarists. However, they can also be beneficial when introduced into more complex or refined aquariums.

Indeed, Mollies can help you keep your aquarium free of algae and relatively clean. They do so by picking and eating the algae that naturally grow on the rocks and plants of your aquarium.

Because of the natural diet, these fish have to receive the nutrients needed through plants and algae when in nature. So, if your aquarium lacks algae, you will need to complete your Mollie’s nutrition with substitutes such as:

  • Spirulina flakes
  • Boiled vegetables (e.i.: spinach) cooked and chopped
  • Commercial food formulated explicitly for Mollies

The Importance of Managing Algae in Your Aquarium

So, now you know that your Mollies are likely to graze on the algae patch in your aquarium. However, they will not be able to clear entire surfaces or significantly reduce algae incidence—especially if you have been dealing with it for a while.

However, before jumping into the many solutions that can help you clean your aquarium, it is crucial to understand algae’s importance in such an ecosystem. Indeed, your aquarium does not need to be completely clean at all times.

Algae play an essential role in promoting a healthy and balanced ecosystem within the aquarium.

Firstly, looking at the natural environment where fish live, it becomes apparent that algae are common. A complete lack of algae in your fishes’ environment can be unnatural and even unhealthy.

Even more importantly, algae are essential to ensure that the water receives enough oxygen. Indeed, just like plants, algae use photosynthesis, which is necessary to help them reproduce, release oxygen during the day, and absorb it during nighttime.

During their photosynthesis process, algae also convert most organic matter into new algae, which reduces the fish waste in the water, making it even cleaner.

Additionally, algae can help to regulate and balance the nutrients and oxygen in the aquarium. So, they can reduce the amount of carbon dioxide in the water, which is necessary for some fish to thrive.

Ultimately, algae are essential for the well-being of the whole aquarium. However, while your fish tank should not be completely free of them, they can quickly get out of control. In this case, some tips can help you naturally reduce the growth of algae. Check them out below.

Other Ways to Manage Algae Growth

Managing the growth of algae is essential to ensure that your fish can live in a clean and healthy environment. Understanding whether you only need to troubleshoot a quick process or eradicate an ongoing issue is crucial.

The tips below can help you limit algae’s growth naturally that won’t harm the fish.

Introduce Algae Eaters

As we have seen above, Mollies eat algae, and they will help you keep your aquarium clean. However, if you are dealing with an ongoing problem, these small fish are not among the most effective ones to have.

Alongside Mollies, you might consider introducing:

  • Twig Catfish
  • Otocinclus Catfish
  • Bristlenose Plecos
  • Siamese Flying Fox
  • Siamese Algae Eater
  • Chinese Algae Eater
  • Whiptail Catfish
  • Malaysian Trumpet Snail
  • Ramshorn Snail
  • Mystery Snail
  • Amano Shrimp
  • Cherry Shrimp

As you can see, several fish, shrimps, and snails are excellent algae eaters and relatively easy to keep and introduce in a fish tank. However, the type you will pick will depend on the type of algae you are dealing with—as well as the kind of fish you prefer to have.

Speaking to an expert aquarist can help you get an idea of the best option for your needs. In turn, this can also help you decide on the right species to introduce for a harmonious environment.

Use Filters

Filters are an excellent way to increase control over the formation and growth of algae. Indeed, they are your primary means to improve the oxygen and flow circulation of the aquarium water. Independently on the type of fish tank that you are designing, filters will be among the most critical components to keep a healthy environment.

Aside from increasing the oxygen flow and ensuring that the water remains clean, they can also help you reduce algae’s growth in the tank. Indeed, adjusting the filter sets allows you to increase its flow rate, moving the water faster, reducing the ability of algae and debris to settle.

Additionally, completing the filter set up with appropriate media will allow better water filtering.

Adjust the Lighting

Lastly, the lighting in your aquarium can encourage the growth of algae. As we have seen above, algae, just like any other plant, will leverage photosynthesis to transform light into energy. While this process will also encourage the reduction of waste, it can promote algae growth and reproduction.

This process is entirely natural and normal, but it can severely impact the ecosystem inside the tank. Reducing the tank’s lighting or swapping the lighting system for a more suitable one will reduce the algae’s growth rate.

Clean the Tank More Often

Regularly cleaning the tank and removing the algae build-up can help the Mollies in your aquarium in their job and help you keep the ecosystem healthy. During this delicate process, ensure you are limiting the stress added to the fish tank’s inhabitants.


Mollies are small fish that are easy to care for and perfect for beginner aquarists. While they are undemanding when it comes down to feeding and tank’s requirements, they require essential nutrients from vegetables and plant matter. Allowing them to pick algae off the aquarium rocks is an excellent way to ensure that they receive the right nutrition to thrive.

At the same time, they are not among the most efficient fish to use as fish eaters. Indeed, they can help you manage the algae in the aquarium, but they won’t clear them and other fishes.