5 Most Common Causes Of Algae In Fish Tanks

Algae is a type of plant that can live in both fresh and saltwater. In fish tanks, algae typically grows on the glass, gravel, ornaments, and plants. While algae are often considered to be a nuisance, they can actually play an important role in the ecosystem of a fish tank. Algae produce oxygen through photosynthesis and help keep the water clean by absorbing excess nutrients.

However, when fish tanks are not properly maintained, algae can quickly become out of control and choke out other inhabitants in your fish tank. It is important to maintain a balanced aquarium in order to prevent algae problems. Algae can sometimes be a sign that something is wrong with your tank and needs to be addressed. We will talk about the causes of algae in fish tanks and  how to get rid of it!

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What Causes Algae Blooms In Fish Tanks?

There will likely always be some algae present in fish tanks, but low amounts of algae are usually harmless. It depends on the type of algae and the amount of growth to determine whether or not an algae bloom is a reason for alarm. Some algae blooms release substances that are poisonous to plants and animals, and large blooms can reduce the amount of oxygen in the water. Identifying the causes for these blooms will help you avoid them in your own fish tank.

Here are some reasons why algae grows in huge numbers.

Too Much Light

One possible cause of algae growth is an aquarium light that is too powerful for the size of the tank, or that is left on for too many hours every day. Light from the sun is another possible cause. Overexposure to light from a window, even while the tank light is off, can promote algae growth.


One of the most common causes of algae blooms is overfeeding. When fish are overfed, excess food falls to the bottom of the tank where it decomposes and releases nutrients into the water. These nutrients encourage the growth of algae, leading to a bloom.

Nutrients are not Balanced

Algae can stunt the growth of your fish tank plants by devouring the nutrients they require to thrive. Algae growth can be stimulated by adding either too many or too few nutrients to your aquarium.

Inadequate Maintenance

Ammonia levels rise to unhealthy levels when organic waste accumulates in a fish tank. Algae will grow rapidly in such conditions. That’s why it’s crucial to keep up with routine checks and adjustments. Reducing organic waste can be accomplished by scrubbing the filter medium and vacuuming the substrate.

Low Circulation

If there isn’t a strong current moving through a fish tank, CO2 and nutrients won’t move well enough to reach all the plants. The filter’s flow rate should be adjusted based on the tank’s volume. Algae has a hard time taking root when plants have plenty of carbon dioxide and nutrients.

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What Causes Brown Algae In Fish Tanks?

A type of microorganism known as diatoms, which number in the billions, creates brown algae. These organisms generate the brown clumps that infest your fish tank, latching to the aquarium’s glass, plants, and equipment. It can be toxic, hazardous, and detrimental to both the fish and plants in your fish tank, so make every effort to keep it under control.

Now that you know what brown algae is, it’s crucial that you learn what triggers its growth.

Filtration Failure

Nitrate levels can also be higher if your tank’s filters aren’t working well. This promotes brown algae growth within your tank, which is an issue for you. The brown algae can be controlled by using proper mechanical filtration to get rid of trash, uneaten food, and fish feces.

Insufficient Fish tank Lighting

The worst thing about brown algae is that it grows in places where green algae can’t. This means that you’ll probably always be fighting one or the other. If your tank has less light, it’s probably too dark for green algae to photosynthesise. But this could encourage brown algae to grow!

If possible, it might be worth thinking about lighting your fish tank better because green algae can be much simpler to get rid of than brown algae.

Nitrate Levels Too High

The waste from the fish in your fish tank can cause nitrate levels to go up. Ammonia is a harmful chemical that comes from things like food waste, fish waste, and plants that are dying. This ammonia is then changed into nitrates by the media in your filter.

Phosphate Levels Are High

Phosphates, likewise, are byproducts of waste decomposition in your tank water. This makes algae grow more, which can make the water unhealthy for your fish to live in. If you follow regular maintenance and the right way to filter, you should be able to avoid harmful levels of phosphate and keep the risk of brown algae under control.

It is important to prevent the brown algae from taking over your tank. If you want to keep a brown algae bloom under control, you need to understand the factors that contribute to it.

What Causes Red Algae In Fish Tanks?

Red algae is not an alga at all, but rather a bacteria, which may come as news to you. If you have red algae in your tank, it will likely start in a tiny area and grow until it covers the entire fish tank. Those who have ever had to deal with cyanobacteria understand how difficult the fight can be. In order to effectively deal with red algae in your fish tank, you must first determine what is causing it

The following are some of the reasons why red algae thrive in your fish tank.

Improper Lighting

You should replace the bulbs in the aquarium’s overhead lighting fixture every six months. The spectrum of the light emitted by light bulbs will shift slightly over time as the bulbs age. Most harmful algae, including Red Algae, flourish in the red spectrum. The risk of red algae growth can be minimized by limiting the amount of time the light is on.

Inadequate Water Flow

Red algae doesn’t do well in fast-moving water. If you look at where the algae is growing in your tank, it is probably in a place where there isn’t much water flow. The quickest way to eradicate and prevent growth is to increase the water circulation in those areas of your tank.

Imbalance Nutrient Level

Red and other slime algae primarily consume phosphates and nitrates as their food sources. Nitrates and phosphates can be found in unfiltered fresh tap water, fish excrement, fish food, and anything that is decaying in your fish tank. Phosphate levels should be maintained at 0.10 ppm, and nitrate levels should be maintained at 5 ppm.

Poor Maintenance

Putting off water changes allows nutrients to accumulate, which slows cyanobacteria development. Algae blooms can be controlled by regular water changes.

Invasive red algae can be a pain to get rid of once they’ve become established in your fish tank. Knowing what makes this red algae grow is the best way to get rid of it. By taking care of your aquarium regularly, you can help keep it clean and free of algae.

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What Causes Bright Green Algae In Fish Tanks?

Bright green algae, often known as filamentous algae, are a diverse group of phytoplankton species (microscopic aquatic plants). Most of the time, they are bright neon green, yellow-green, or brownish-green as they die. In the beginning, the filaments will attach themselves to the walls, plants, and other things in the fish tank. They will eventually break apart and float away as mats.These algae don’t have roots, so they get their food from the water.

Some of the factors that lead to bright green algae are:

Carbon Dioxide (CO2) Imbalance

The main cause of filamentous algae is an imbalance in the levels of carbon dioxide in the water. When there is too much carbon dioxide, it causes the water to become more acidic. This acidity makes it difficult for fish to breathe, and it can also damage their scales. In addition, the acidity can make it difficult for plants to grow. As a result, an imbalance in carbon dioxide levels can lead to an overgrowth of filamentous algae in your fish tank.

Excessive Light

Excessive light is one of the most common causes of filamentous algae. Algae need sunlight to grow, but too much sunlight can cause them to grow out of control. When this happens, the algae may form long, stringy mats that can smother other inhabitants in your fish tank.

High Levels of Nutrients

Another common cause of filamentous algae growth is high nutrient levels. When nutrients like nitrogen and phosphorus are present in excess, they can promote the growth of algae blooms.

What Causes Blue Green Algae?

Blue-green algae are actually bacteria that have qualities similar to algae and other plants. These bacteria are cyanobacteria – cyan means “blue-green” – and are commonly found on land and in lakes, rivers, ponds, and in estuaries and marine water. Cyanobacteria is very easy to spot in fish tanks. Blue green algae is easily recognizable by its dark green hue, slimy texture, rapid growth, and distinct odor. At high concentrations, it can destroy an aquarium’s delicate environment. Toxins produced by cyanobacteria are bad for fish, shrimp, and plants.

Cyanobacteria can reproduce quickly in fish tanks due to:

Abundant Light

The blue-green algae can also bloom when there is an excessive amount of light in a certain section of the fish tank. A good place for cyanobacteria to grow is in a corner of your tank that receives nearly consistent light.

Slow Water Circulation

Blue-green algae can grow in your fish tank if the water moves slowly. Moving water keeps it from getting stagnant. This is also true of ponds and lakes. Those with a fast moving current have cleaner water than those with a slow moving current.

High Levels of Nutrients

When there are a lot of dissolved wastes and nutrients like nitrate and phosphate in the water, this organism tends to grow out of control. In particular, phosphate is a major factor in the expansion of cyanobacteria. There could be an accumulation of trash and nutrients because of infrequent water changes, poor upkeep, or overfeeding.

What Causes Black Beard Algae?

Common aquarium algae includes black beard algae (Audouinella sp.). Although it prefers the leaves of slow-growing fish tank plants, Black Beard Algae will colonize just about any tank surface. It consists of incredibly thin strands or densely clustered tufts. It looks like a beard, which is how it got its name. It typically seems black, although it can also be a vivid green, a bluish green, or even a dark green.

Black bearded algae does not poison the water or take nutrients from plants. But it can kill the plant if it completely covers it. It may be challenging to totally prevent exposure to Black Beard Algae. Knowing what causes its existence is crucial for preventing its growth.

Here are the main causes of Black Beard Algae growth:

Too Much Light

When fish tank lighting levels are too high, black beard algae thrives. It is common for it to thrive and grow rapidly in conditions of high intensity or prolonged exposure to light. If the tank is in direct sunlight, it might be a good idea to move it or put something over it to block the sun.

Excessive Amounts of Nutrients

When there is an abundance of nutrients in the water, such as nitrates, Black Beard Algae grows. When controlling the amount of nutrients in the tank, there are a few things to keep in mind. You need to change the water often and make sure to avoid overfeeding. If the fish are given too much food, they will make a lot of waste.

Low Carbon Dioxide

Growth of Black Beard Algae has been linked to low or fluctuating CO2 levels. The aquarium plants will be able to absorb more nutrients in the water if CO2 levels in the tank are increased and stabilized. It can more effectively compete with algae.

What Causes Green Hair Algae?

Green hair algae can contaminate both freshwater and saltwater tanks. This kind of algae develops into long, hair-like strings, as the name would imply. Long threads of this sort of algae can really entangle fish and invertebrates in your tank, making it impossible for them to move or feed, despite the fact that they mostly cause a visual problem. The algae can also spread quickly and become highly obtrusive. Although removing green hair algae is a difficult task, prevention is the key to preventing its recurrence.

Green hair algae can grow too much for many reasons. What caused the outbreak and what needs to be done to stop it from happening again. The following are major causes:

Excessive Amounts of Sunlight

If your tank has too much light, hair algae will spread even more quickly. To avoid this, turn down the brightness of the lights in the fish tank. Green hair algae won’t spread quickly in your tank if you turn down the light.

Excess Nutrients

Green hair algae need phosphates and nitrates to stay alive. So, if there are a lot of phosphates and nitrates in your tank, green hair algae are very likely to grow there. This means that you need to lower the levels of phosphate and nitrate if you want to get rid of hair algae. Phosphate levels should be at.05 ml/l and nitrate levels at 10 ml/l.

Imbalance Carbon Dioxide

The green hair algae in your fish tank can also be caused by carbon dioxide that is not stable. The CO2 level in the tank should be between 20 and 30 ml per liter.

What Causes Algae In Planted Tanks?

Algae that cause problems are a major problem for everyone with a planted fish tank. Algae is annoying and looks bad, and the ways to get rid of it vary greatly from aquarium to aquarium. The prevention of algae starts on the first day a planted tank is built. Knowing what causes algae to grow in planted tanks helps you deal with it effectively.

Here are the main reasons why our planted fish tanks get algae:

There Aren’t Many Good Microorganisms in the New Environment

A fresh setup usually has algae growth in the first two to three months. This is because the nitrification cycle, which converts ammonia to nitrogen gas, is not yet fully functional in a newly planted fish tank. When there is too much ammonia, algae will grow in large numbers. Algae suffocates plants by blocking light and preventing nutrients and CO2 from getting to the leaves, which kills the plant.

Low Water Circulation

It is important for any planted fish tank to have strong water flow so that the nutrients and CO2 can move around the aquarium and reach all the plants. The recommended flow rate for filters and powerheads to adequately circulate an aquarium is roughly 10 times its volume.

Insufficient Surface Agitation

Keeping the aquarium’s surface agitated helps keep the water oxygenated and free of scum, or an oily film that can accumulate on the water’s surface. Too much surface movement, on the other hand, will make it more likely that the CO2 will escape. The usage of an air pump is encouraged, but only when the lights are out.

Inadequate Aquarium Maintenance

Without regular aquarium cleaning, organic waste accumulates, producing an environment favorable to the growth of algae in the form of ammonia. Organic waste won’t build up as much if the substrate and filter media are regularly vacuumed and cleaned.

What Causes Algae On Aquarium Glass?

Aquariums are a beautiful addition to any home, but they can be a pain to keep clean. One of the most common problems is algae growth. Algae can start growing on the glass of your aquarium in just a few days, and it can be really tough to get rid of. Algae need three things to grow: light, water, and nutrients. If your aquarium has any of these factors in abundance, then you are more likely to have a problem with algae growth.

Here are the most common reasons why algae grows on aquarium glass:

  1. There is too much light. Algae thrive in sunlight, so if your aquarium is in a sunny spot or you have strong artificial lighting, this can be a problem.
  2. Water temperature is too warm. Algae love warm water, so if your aquarium is in a warm room or near a heat source, this can also cause algae to grow.
  3. There are too many nutrients in the water. This can be from overfeeding your fish, using too much fertilizer, or having an overabundance of algae in the tank.

How to Prevent Algae in Fish Tanks

Every fish tank owner will have to deal with algae growth at some point. Algae growth is normal and healthy in small amounts, but too much algae growth is ugly and can hurt fish and plants. Algae need water, light, and nutrients to grow, just like any other plant. When there is too much of any of these factors, algae can grow wild.

Here are some things you can do to stop this overgrowth and, in many cases, even turn it around.

Don’t Feed Fish Too Much

We’re sometimes tempted to feed our fish twice or three times a day, which is fine if your fish eat all the food in a few minutes. Overfeeding, which means giving too much food, causes problems. Most algae get the nutrients ammonia and phosphate from overfeeding. Algae thrive on both uneaten food and fish waste.

Manage the Lights in the Aquarium

Put your lights on a timer to make them go on and off like day and night, and stick to it. Plant aquariums should have lighting on for 10-14 hours daily, whereas terrariums should have lighting on for 6-10 hours daily. Also, change the bulbs at least once a year because algae will likely grow in places where the light is weak.

Change the Water in an Aquarium Often

Your closed fish tank system, on the other hand, needs regular water changes to get rid of excess nutrients. The best amount is 10% once a week. It’s also a great opportunity to remove the muck and decaying vegetation from your gravel.

Check Your Tap Water

You should always check the quality of your tap water before making any modifications, as it may already include chemicals that promote the growth of algae. If the test shows that there are a lot of phosphates or other things that make algae grow, you won’t be able to get rid of algae by changing the water until you get a RO (reverse osmosis) unit or a tap water filter.

Keep Your Aquarium’s Filter Media in Good Shape

Choosing the right filter media can make a big difference in the amount of phosphate: Poly Filters will get rid of phosphate and heavy metals, and the way they change color shows if there are any problems. Change the mechanical and chemical media in your aquarium once a month. This is because as the media wears out and fills up, it can release bad things back into your aquarium.

Increase the Competition With Plants

The more plants you have in your tank, the less likely it is that algae will take over. Algae and plants compete directly for light and nutrients, and plants usually win if the conditions are right.

Stock With Algae-Eating Fish

Put fish in your neighborhood to work cleaning up. Cory Cat, a type of catfish, swims around the bottom of your aquarium and eats leftover fish food and plant leaves before they can rot and make harmful ammonia and nitrite.

How Do I Get Rid of Algae in My Fish Tank?

A fish tank has the potential to be a stunning piece of living art, a thriving aquatic ecosystem, and a healthy home for swimming buddies; yet, if the tank is too dusty, muddy, or covered with algae, it will not be any of these things. As an owner of a fish tank, you are probably familiar with the seemingly never-ending battle against the growth of algae. Thankfully, there are methods that you can take to eliminate algae and help keep it under control.

Pick an Appropriate Filter

The filter in your tank will keep the water clean by removing any trash or debris that may have gotten into the system. Select the best filter your money can buy, keeping in mind the tank’s size and the filter’s recommended flow rate. The best filter is one that incorporates multiple types of filtration, including chemical, mechanical, and biological processes.

Give Your Fish the Right Amount of Food

Serve only the finest food to your fish, since this will aid in their digestion, and feed them in accordance with a rigorous timetable. In order to prevent the tank from becoming foul, any food that has been sitting there for more than 5-10 minutes should be strained out and thrown away.

Regularly Replacing the Water

Regular small water changes can assist maintain a clean tank by replacing old, stale water with fresh, new water. Keep your fish happy and healthy by just changing 10-20% of the water every 2 weeks.

Add the Cleanup Team

Some fish species can eat algae, making them useful tankmates. Maintain a few of these tank occupants to keep things looking clean and fresh.

Clean the Glass

Use a scraper or a razor blade to carefully cut away the algae from the tank’s walls. Keep the algae development to a minimum by scraping the sides of the tank on a regular basis, and you’ll be able to see the tank’s full range of colors and textures with more clarity.

Trim Fish Tank Plants

Aquatic plants are not only aesthetically pleasing, but also serve an important purpose by providing food and cover for your fish. But if you see any grasses or leaves turning brown or rotting, cut away the dead parts to keep the tank clean.

Clean your Fish Tank Props

Structure and whimsy can be added to your aquarium with the help of accents like rocks, logs, castles, sunken ships, and other decorations, but they won’t look as good if they’re coated in algae. To prevent the growth of algae and maintain their cleanliness, simply rinse them with hot water and wipe them down.

Clean up the Gravel

The bottom of your aquarium will eventually become covered with waste products, lost scales, uneaten food, discarded plant matter, and other rubbish. A weekly gravel vacuum will maintain the gravel clean, brighten the tank, and reduce the buildup of harmful particles.

Why Is Algae Bad For Aquariums?

Algae is often seen as a nuisance in an aquarium. It can grow quickly and overtake the tank, making it difficult to keep clean. If you are having trouble with algae in your aquarium, read on for seven reasons why algae is bad for aquariums and how to keep your tank clean!

Algae can cause problems in an aquarium for a number of reasons.

Algae Can Block Out the Light That Is Necessary for Plants to Grow

Algae grows quickly and can spread rapidly, quickly covering the glass of the aquarium and blocking out the light that plants need to grow. As a result, plant growth can be stunted, and eventually, the plants may die.

It Can Consume Oxygen That Is Necessary for Fish to Breathe

In aquariums, algae can quickly become a problem, as it can grow unchecked and consume vital resources like oxygen and light. Fish rely on oxygen to breathe, and if the levels in the water become too low, they may suffer from stress or even die.

It Produces Toxins That Can Be Harmful to Fish and Other Aquatic Creatures

These toxins can build up in the water. It can cause problems with the immune system, leading to disease and illness.

Algae Can Negatively Impact Water Quality by Causing an Increase in Ammonia Levels

When algae grow out of control, they can quickly deplete the dissolved oxygen levels in the water. This can lead to an increase in ammonia levels, which can be harmful to fish and other aquatic creatures.

It Can Clog Filters and Other Aquarium Equipment

It makes it difficult to keep the fish tank clean. It can also grow on the glass walls of the tank, making it difficult to see inside.

Algae Can Be a Host for Harmful Bacteria and Parasites

It poses a serious threat to the health of your fish. Algae can act as a host for harmful bacteria and parasites, which can infect your fish and make them sick.

It Can Make an Aquarium Look Unsightly

Algae can be difficult to remove and can cause your aquarium to lose its aesthetic appeal.


Why Is Algae Good For Aquariums?

Actually, algae aren’t all bad. Algae are important to your pond or fish tank in many ways. Carbon and nutrients cycle because of algae. In aquatic systems, they are like plants in terrestrial systems. They are at the bottom of the food chain. They use light as a source of energy to turn carbon dioxide gas into cell tissue. And just like plants, algae make oxygen.


Algae is a natural part of any aquatic ecosystem. While it can be unsightly, it also has some benefits. There are different types of algae and each has its own causes and effects. Fortunately, there are ways to prevent algae from growing in your tank and harming your fish. By understanding the causes of algae blooms and taking steps to stop them, you can keep your tank healthy and your fish happy.