How to Get Rid of Algae in Your Fish Tank Effectively

Algae is a natural phenomenon in water bodies, which means home fish tanks are no exception. It’s common to find algae growing in aquariums, but if left unchecked, those tiny green patches and clumps can quickly overrun the tank and cause all sorts of problems for your fish.

When algae overgrows, it competes with fish for oxygen, messes up the pH level, blocks water filters, and even suffocates fish by clogging their gills. This can weaken your fish, make them sick, and even cause sudden death. For these reasons, you need to know how to keep your aquarium’s algae under control at all times, which I’ll teach you below from personal experience rearing African catfish in my fishery. 

Key Takeaways

  • Algae overgrowth can harm fish by depleting oxygen levels, disrupting PH balance, clogging fish gills, and blocking tank filters.
  • There are different types of algae. Each one has its benefits and drawbacks, and they may indicate a problem with the tank water.
  • Your options for eliminating algae include algae eaters, algaecide, light reduction, and cleaning the tank water.
  • Preventing algae overgrowth is easier than getting rid of them. You can achieve this by proper nutrient control, limiting light exposure, keeping live plants, and regular tank maintenance.

Understanding The Different Types of Algae 

Not all aquarium algae are equal. Each algae type has different characteristics, benefits, and potential harms it can cause to your fish. Below, we briefly discuss these algae types, but you can learn more about them in our comprehensive guide to aquarium algae.

Green Algae

Green algae is the most common type and is found in water with good quality. It’s harmless, and fish will readily eat them. But, it multiplies quickly and must be controlled to protect fish.

Blue-Green Aquarium Algae

This type of algae isn’t a plant but rather a type of cyanobacteria. You’ll identify it by its blue-green color, sheet-like growth pattern, and musky odor. Blue-green algae can indicate too much light, excess organic waste, and high phosphate levels. 

If left to overgrow, it’ll form a thick layer that can be tricky to remove as algae eaters often avoid it.

Brown or Red Aquarium Algae

Brown or Red Aquarium Algae

Brown or red algae indicate high levels of silica and phosphates and are commonly found in new tanks. The good news is this type of algae is harmless, easy to remove, and will often go away on its own as other plants will naturally consume the excess phosphates and silicates.

Staghorn Algae

Staghorn Algae

Staghorn algae is hair-like, and usually grows around equipment like filters. This makes it hard to remove mechanically, so you might need to use bleach or algaecide to remove them.

Fuzz Algae

Fuzz Algae

Fuzz algae isn’t indicative of bad water, and luckily, doesn’t threaten fish. Two similar-looking algae species with minor differences from the fuzz algae are the hair algae and beard algae.

Thread Algae

As the name implies, this algae forms thread-like strands that are long and thin and don’t form patches. The presence of thread algae indicates high levels of iron.

What Causes Algae Growth?

Understanding the root cause of algae growth will help you prevent overgrowth or stop its regrowth after getting rid of it. I’ve found from experience that excessive nutrients and light are the top two causes of algae overgrowth in fish tanks. 

That said, here are 6 common causes of algae growth:

  1. Overfeeding: Overfeeding fish leaves behind excess nutrients and waste for algae to thrive on.
  2. Excessive light: Algae undergo photosynthesis and will thrive under intense light for long periods.
  3. Nutrient imbalances: Some types of algae thrive when there are nutrient imbalances, like high levels of nitrates and phosphates.
  4. Infrequent tank cleaning: Without frequent tank cleaning or maintenance, you’ll give algae room to thrive and grow to a point where they increase rapidly.
  5. Poor tank filtration: When the filtration system stops working properly, waste and nutrients accumulate in the tanks, which can encourage algae growth.
  6. Overcrowded aquarium: In an overcrowded tank with lots of fish, there will be high amounts of waste, encouraging algae growth.

How to Get Rid of Algae in Your Fish Tank

Now, let’s discuss how to get rid of algae in your fish tank. My go-to method for eliminating algae is algaecide because it’s quick, effective, and doesn’t require extra aquatic inhabitants. But below, I’ll cover four key ways of getting rid of algae safely and effectively:

Algae Eaters

Algae-eating fish like the Siamese, bristlenose pleco, and twig catfish offer an affordable, safe, and effective way to get rid of algae in fish tanks. Algae eaters save you manual labor as they work around the clock to keep algae at bay without your input.

In addition, algae eaters get rid of algae without the risk of contamination from chemical products. And, they don’t require a recurring purchase or regular application.

But some algae eaters can grow too big, become aggressive with age, or threaten other aquarium plants, so you need to understand the best algae eaters for getting rid of algae, which ones are compatible with your aquarium inhabitants, and how to take care of them. 

Algaecide Chemical products

Another effective method for getting rid of algae is to apply algaecide, which is a bucket term for chemicals made to kill algae without harming your fish or plants. The algaecide is applied directly into the tank water without removing the fish or plants, making the process convenient.

Having said this, you’ll still need to take extra precautions as the chemicals can still affect aquatic life. In addition, there are different types of algaecide, each with its unique mechanism for killing and controlling algae.

We recommend the following algaecide chemical products for checkmating algae in your fish tank:

API ALGAEFIX Algae Control

API ALGAEFIX Algae Control Solution is fast-acting and effective for killing and controlling the growth of multiple types of algae. Moreover, API ALGAEFIX won’t harm your fish or plants and is safe for use in freshwater, saltwater, and reef aquariums.

Algaecide like this helps to reduce the frequency of aquarium maintenance and eliminate the need for mechanical algae removal. The only downside is the API ALGAEFIX Algae Control can’t be used with freshwater crustaceans like shrimp, lobsters, and crabs.

Crystal Blue Copper Sulfate Algaecide

The Crystal Blue Copper Sulfate Algaecide contains 99% copper sulfate pentahydrate and effectively controls most algae species including filamentous and string algae. This product was designed specifically for larger ponds but may be suitable for tanks when used in smaller amounts.

The Crystal Blue Copper Sulfate Algaecide is effective, works fast, and goes for a reasonable price (around $30 USD). However, this product can’t be used for fish that are sensitive to copper sulfate products like goldfish, koi, grass carp, or trout. 

Note: Avoid excessive use of algaecide as eliminating too many algae at once can deplete oxygen too quickly and harm your fish.

Light Reduction

Like other plants, algae get food from light through photosynthesis. And the more light algae gets, the better they thrive. So, reducing the amount of light entering your tank will help control algae overgrowth.

You may have to induce a total blackout for a few days for this method to be effective. However, you must be careful as fish need a consistent day/night cycle to stay healthy. 

Instead, you can keep the lights dim and less intense for shorter periods to discourage algae growth. Additionally, avoid direct sunlight as it promotes rapid algae growth.

Cleaning The Tank

Getting rid of algae in your tank can be as straightforward as following a regular aquarium maintenance routine that includes: 

  • Scraping, scrubbing, and washing the algae off glass, rocks, decorations, filters, and other hard surfaces
  • Vacuuming the gravel and substrate to remove algae, and
  • Dipping plants in a 5-10% bleach solution to kill algae stuck on the leaves and stems. But be sure to thoroughly rinse the plants as bleach is toxic to fish.

🐠Be sure to check out our ultimate guide to aquarium maintenance for more helpful information on maintenance equipment, tips, and mistakes to avoid.

How to Prevent Algae Growth

Preventing algae from overgrowing will save you time, effort, and resources spent on getting rid of them. Even after getting rid of algae, you’ll still need to prevent them from returning and taking over the fish tank. I’ve noticed that keeping nutrients in check goes a long way in preventing algae overgrowth in my fish tank even when sufficient light is available.

Below are some practical ways you can apply to prevent algae from overgrowing in aquariums:

Nutrient control

In the aquarium, fish and plants tightly cycle the nutrients from fish food and waste. But when you overfeed fish, it leaves an excess of nutrients which algae then feeds on and overgrows.

To discourage algae overgrowth due to excessive nutrients, only feed your fish the amount they can consume and nothing more. If you notice excess food on the tank floor bed and the fish hasn’t consumed it after five minutes, that’s a good sign of overfeeding.

At this point, you need to clear the excess food before algae can feed on them. Your options include changing the tank water or using phosphate and nitrate resins to soak up the excess nutrients. As a preventative measure, only feed your fish in small bits and wait until there’s no more food before adding more.

Limiting light exposure

Fish don’t need as much light as plants. They only need enough to maintain a healthy circadian rhythm, and dim lights for 8-10 hours daily will do.

For these reasons, avoid direct sunlight, use only dim aquarium lights, and set a timer to ensure the lights don’t stay on too long. In essence, the lesser the light available, the harder it will become for algae to thrive and overgrow.

🐠Here’s how to choose the best lighting for your fish tank.

Keep live plants

Live plants help to prevent algae overgrowth by absorbing excess nutrients and starving algae of the nutrients they need to thrive. Plants like wisteria, hornwort, and teardrop effectively use excess nutrients and control algae growth.

Regular maintenance

It goes without saying that your fish tank needs regular maintenance, and this applies to preventing algae overgrowth. This regular maintenance basically involves changing the tank water and cleaning the aquarium as frequently as needed.


What Naturally Kills Algae in a Fish Tank?

The only natural way to effectively kill algae is by either starving them of food (light and nutrients) or by introducing algae eaters that consume the algae. Besides this, your only other option for killing algae is artificial chemical products called algaecide.

How do I Reduce Algae in my Fish Tank?

You can reduce algae in fish tanks using multiple methods including: 

  • Algae eaters
  • Algaecide products
  • Light reduction
  • Proper nutrient control
  • Live plants to compete with algae
  • Manual removal with regular tank maintenance.

Why Do I Have So Much Algae in My Fish Tank?

The most common reason why you have too much algae in a fish tank is due to excessive nutrients and light which algae feeds on and overgrows.

Is Algae Bad for Fish Tanks?

Algae isn’t necessarily bad for fish tanks unless it overgrows, which becomes a problem for your fish. So while you may find some harmless algae in your fish tanks, you’ll need to keep it in check before it becomes a nightmare for the aquarium inhabitants.

Can Too Many Algae Kill My Fish?

Yes, too many algae can kill your fish by competing with them for oxygen, suffocating them by clogging their gills, and raising the pH to unhealthy levels, leaving them prone to diseases.

Keeping Algae In Check

Algae overgrowth can quickly become a nightmare, especially when fish start falling ill. Luckily for us fish owners, there are multiple ways to effectively eliminate them, which include algae eaters, algaecide products, manual removal, light reduction, and proper nutrient control.

And even if you’ve gotten rid of them or haven’t experienced algae overgrowth in your tank yet, you’d still need to actively prevent it by limiting light exposure, avoiding nutrient imbalances, or keeping live plants.

Have you experienced algae overgrowth in your aquarium? How did you handle it? Kindly share your experiences in the comments section, and be sure to share this article with fellow aquarium owners!

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