Written by Team Buce Plant and The Aquarium Home

Why does your aquarium have algae? Unfortunately, that’s a question new – and even experienced – aquarium owners ask themselves often.

Algae can quickly spread in aquariums, covering surfaces, obstructing views, and competing with aquarium plants for resources. Different types of algae, like green hair algae, black beard algae, and brown diatoms, grow in various conditions. Each type needs its control method. To keep your tank healthy and aquarium plants looking good, it's important to understand why algae appears.

So why does algae appear in aquariums, what are the common types, and how can you eliminate it?

The 3 most common reasons aquascapers struggle with algae are 1) a lighting imbalance, 2) excess nutrients, or 3) poor water circulation and quality. If you want to learn how to get rid of algae, keep reading!

Algae is not bad for your fish tank

Although algae can be unsightly, but in most cases, it's not harmful. Algae play an essential role in the aquarium ecosystem, supporting the food chain and helping maintain a healthy biological balance that benefits the overall aesthetic of a planted tank.

Studies also suggest that actively growing plants can release compounds (allelopathy) that naturally inhibit algae growth, supporting a stable ecological environment. As a tank matures, it’s common for various algae types to appear and eventually settle into a natural balance, marking the aquarium's progression toward stability.

Algae are simple organisms that photosynthesize just like plants, but they lack specialized structures such as roots, stems, or leaves. Algae also help produce oxygen and serve as a food source for some aquatic life.

While algae itself isn’t harmful, too much can become a real issue in the aquarium. For example, if algae begins covering plant leaves, this may block light and limit the aquatic plant’s ability to photosynthesize.

Algae itself is not dangerous to your aquarium, but an abundance of it could be a sign of imbalance in your tank. Keeping things in check is key.

Algae outbreaks happen because your aquarium is unbalanced

Here's another quick rundown of the three main causes behind algae outbreaks: lighting, nutrient levels, and water imbalances—sometimes it's a combination of all three.

Pinpointing the root cause of your algae problem can help you take the right steps to address it and prevent algae from taking over your aquarium.

1. Algae thrives in light. They’re photosynthesizing organisms, so if you’re providing too much light either directly or indirectly (i.e. aquarium LED light or direct sunlight), you’re providing the ideal environment for algae to take hold.

To fix this, avoid setting your aquarium where it gets sunlight. If you’re using LED lights, only keep them on for a max of 10 hours a day, although a recommended 6-8 hours is even better.

2. Algae loves excess nutrients. These nutrients come from liquid fertilizers, fish waste and food, and decomposing organic materials.

The best way to deal with these excess nutrients is to avoid overfeeding and keep up with your weekly water changes—consistent maintenance is your best weapon against algae.

3. Algae loves imbalance. Swings in pH, poor water quality, fluctuating lighting levels, and inconsistent water changes are algae’s best friends. A confused ecosystem gives algae room to grow, so try to keep parameters constant and don’t make drastic changes to your aquarium.

5 types of algae and how to get rid of them

Five algae species are the most commonly dealt with by aquarists. Let’s cover 5 common types and how you can eliminate them from your aquarium.

1. Hair Algae

As the name implies, hair algae appears in long, green strands. It grows quickly on aquatic plants and other surfaces. Once it establishes itself, it can be hard to control. Hair algae is generally caused by excess nutrients (like iron), too much lighting, or not enough nutrients to match the lighting period. Luckily, prevention and removal are pretty easy.

While plants rely on nutrients like nitrogen, phosphorus, and potassium, an excess or deficiency can trigger algae growth instead. Keeping nutrients balanced is key: avoid over-fertilizing, especially with iron-heavy fertilizers, and ensure plants receive the nutrients they need to outcompete algae. Test your water regularly and adjust nutrient levels if you notice imbalances that could encourage hair algae to flourish.

To prevent algae outbreaks, make sure your lighting isn’t too intense or on for too long—find the right balance for your aquarium plants. The sweet spot for aquarium lighting is typically between 6-8 hours a day. Also, stick to regular weekly water changes to avoid nutrient buildup, which algae loves. 

Once hair algae takes hold, it must be manually removed. You can use a toothbrush to scrub it off surfaces. Alternatively, you can use a siphon hose to pull it out by hand during water changes.

2. Brown Algae (Diatoms)

Brown diatom algae is a dusty, brown film that often appears on aquarium plants, glass, and substrate. Newly-setup aquariums commonly experience it, and you can easily get rid of it.

This type of algae feeds on excess phosphorus and silicates, which are more abundant in new tanks. As your aquarium ages, your plants will absorb these nutrients, and the algae typically fades on its own.

To remove it from your tank quickly, use a toothbrush to scrub it off plants or decorations. Use a glass scraper to clear it from the tank walls. Another tip is to add algae eaters like shrimp and snails who love eating this stuff, especially Amano Shrimp.

For more information on diatoms and how to keep this algae at bay, click to read How to Get Rid of Brown Algae (Diatoms) in the Fish Tank.

3. Blue-Green Algae

This isn’t actually algae, it’s cyanobacteria. This is the bane of many aquarists' existence for good reason. The cause of cyanobacteria in aquariums isn’t fully understood, but a few common factors are known to encourage its growth.

Cyanobacteria tends to appear in aquariums where a mix of low water flow, excess organic waste, imbalanced nutrients (especially high phosphates), and long light exposure occur. Low nitrates and reduced oxygenation can also create favorable conditions, allowing cyanobacteria to compete effectively with algae. Because each tank is different, managing these aspects can go a long way in minimizing cyanobacteria growth.

It’s difficult to fully remove manually, so some aquarists use anti-bacterial treatments specifically designed for fighting cyanobacteria, like Dr. Tank BGA Zero Tablets. 

Then once it’s on the decline, troubleshoot to see which nutrients your aquatic plants need more or less of. Another tip is to redirect the filter output and the BGA goes away on its own, since it’s most common in dead spots.

For more information on diatoms and how to keep this algae at bay, read How to Get Rid of Cyanobacteria in Aquariums.

4. Black Beard Algae

Black beard algae (BBA) is indeed a stubborn type of algae in aquariums, typically appearing as dark, fuzzy patches that are challenging to remove manually. It tends to thrive under conditions like fluctuating CO2 levels, excess organic waste, and lighting imbalances.

When CO2 levels in the planted tank are inconsistent, BBA can more easily establish itself, as the plants become stressed and less effective in competing for nutrients. High light exposure and excess nutrients, particularly phosphates, may also contribute to its spread, though light management alone may not prevent it.

For removing BBA, you can start by trimming any affected plant leaves and disposing of them outside the tank. For hard surfaces like rocks, wood, or other decorations, spot treatment with 3% hydrogen peroxide is often effective. Applying hydrogen peroxide directly to BBA during a water change and letting it sit for a few minutes can oxidize and weaken the algae, making it easier to remove.

Also, Dr. Tank BBA Remover Tabs or SL-Aqua Z3 BBA Remover are both effective against stubborn BBA. When used in combination with consistent tank cleaning maintenance, visible algae is reduced and overall health is improved.

For more information on BBA and how to get rid of it, read How to Get Rid of Black Beard Algae in the Fish Tank.

5. Green Water

If your tank water has taken on a cloudy green tint, this is most likely green water algae—free-floating, single-celled organisms that grow quickly in the right conditions. These blooms can be sparked by factors like bright or prolonged lighting, spikes in ammonia, and nutrient imbalances, especially in newer tanks.

Green water can be stubborn, as regular water changes rarely remove it entirely. To curb it, some options include a “blackout” period, reducing light intensity, or using UV sterilization to neutralize the algae cells. Each method can help restore clarity without affecting the tank’s overall balance too drastically.

For more information on Green Water and how to get rid of it, read How to Get Rid of Green Water in Aquariums.

Focus on strong plant growth – not just algae prevention

Algae is the result of an imbalance in your aquarium – most often between lighting and nutrients. Your focus shouldn't only be on preventing algae but also your aquarium plant growth and health. Healthy plant growth is the best way to combat algae. To recap, here are tips to balance an aquarium and minimize algae:

• 1. Control Lighting Duration: Limit aquarium lighting to 6-8 hours per day. Excessive lighting promotes algae growth, so setting lights on a timer can help keep a consistent schedule.
• 2. Maintain Nutrient Balance: Use an all-in-one aquarium fertilizer for plants, and adjust the dosage based on plant growth and tank conditions. Avoid over-fertilizing, which can fuel algae growth.
• 3. Regular Water Changes: Replace 20-30% of the tank water weekly to remove excess nutrients, organic waste, and algae spores, which helps maintain overall water quality.
• 4. Introduce a Clean-Up Crew: Adding algae-eating shrimp, snails, or fish can help manage algae naturally by grazing on it before it becomes a problem.
• 5. Keep Water Flow Consistent: Good water circulation prevents dead zones where algae can thrive, ensuring nutrients and oxygen are evenly distributed throughout the tank. Make sure you have a quality filter that is large enough for your aquarium.
• 6. Use Natural Algae Control: Green Water Labs Algae Control is the first all-organic, plant-based treatment effective against many types of aquatic algae. It works to both prevent and treat algae in the aquarium. Dose weekly for an added layer of protection in your tank.

But despite our best efforts, algae might always be present in our aquariums – it’s just a matter of keeping your plants strong enough that algae never takes over. That’s why aquarists use clean-up crews like shrimp, snails, or plecos to keep it under control!

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