Let’s talk about algae, you know, the green or brown stuff that makes your pretty tank ugly.

The positive side of algae is that its appearance means you have created livable conditions for an organism. Congrats! The negative side is that it looks unsightly and may harm your aquarium plants.

Before we get into algae control methods, let’s explore some causes of algae in fish tanks.

What Causes Algae in Fish Tanks

Algae is naturally occurring in almost every water source, even your tap water so don’t blame yourself completely for the green mess in your tank.

And the main reason you have algae in your aquarium is that you created a great place for it to live.

That means your water supports life. Congrats!

Completely eliminating algae should not be the goal because that would mean your tank is unlivable for other creatures as well.

But controlling algae to the point where you hardly notice it is completely doable, even without chemicals.

Some of the reasons for an explosion of algae in your aquarium might include:

1) Tap water with lots of nutrients and minerals

If your tap water contains high amounts of phosphate, iron, or nitrate, then algae is going to thrive. If possible, consider using water from a source that does not contain these algae fueling nutrients.

2) Too Much Light

Algae likes a lot of light. If you are keeping your aquarium light on constantly, you may be helping algae out compete your plants for nutrients.

Sunlight also seems to cause algae blooms. If your aquarium is positioned near a window that gets natural sunlight, you may want to find a darker location for it.

Natural sunlight often creates what aquarists call “green water,” , which is actually healthy for your fish and invertebrates but makes your tank look like a disaster.

If you are concerned that reducing light will harm your aquarium plants, don’t worry, aquarium plants only need about 6 to 8 hours of light for photosynthesis so buy a timer for your aquarium light and don’t let algae see the light of day (pun intended).

3) Overfeeding Your Fish

Fish food contains nutrients like phosphates and iron so excess or uneaten food provides algae with nutrients. Removing uneaten fish food and performing a water change after a heavy feeding will help prevent algae from proliferating.

Types of Freshwater Aquarium Algae

Before you start your crusade against algae, you should know that there are quite a few different types of algae and even some organisms that look like algae but are in fact bacteria.

1) Blue Green Algae or Cyanobacteria

This brownish green blob often hangs out on the substrate. While it looks like a mass of slimy algae, it is in fact a colony of bacteria that have the ability to photosynthesize.

Blue green algae is often smelly but can easily be removed by scraping it off glass and removing bigger chunks with tweezers.

2) Brown Algae

In freshwater tanks, what we call brown algae is actually a diatom. These brownish diatoms usually appear in force between the first and third week of a newly setup tank.

Brown algae will coat everything in frown layers of film. Plant leaves, substrate, heaters, filters, and every inch of aquarium glass may turn brown in smaller tanks.

At this point a new aquarist might think, “it’s over,” but there is no need to despair.

Brown algae thrives on silicon dioxide, and other nutrients, and pretty much has those to itself in the first few weeks of a new tank.

But, other species of algae will begin to establish themselves after the third week and compete with the brown algae for nutrients.

The result is that the brown algae will die back and your tank will look great again.

Adding snails and aquarium plants will also help speed up brown algae’s retreat.

3) Green Thread Algae

Green thread algae looks like wispy threads hanging from the top of aquarium plants.

Removing may only require moving your finger or a pair of tweezers in a circular motion over the algae and then pulling it up and out of the tank.

4) Green Hair Algae

Green hair algae can appear quickly and may cover plants with it’s spikey looking filaments.

Removing green hair algae by hand is a challenge but can be done. Snails, like nerites, and aquarium shrimp like Amano shrimp may help curb the spread of this algae.

5) Staghorn Algae

Staghorn algae looks like a big chunk of hair. Not to be confused with green hair algae, Staghorn algae is a pale grey is color and tends to attack itself to aquarium décor, equipment, and slow growing plants like Java fern.

6) Green Spot Algae

Green spot algae appear as crusty green spots on aquarium glass and plants leaves.

Green spot algae tends to thrive under strong lighting so reducing the amount of hours your light is on may help with long term control.

Removing it from aquarium glass may require a razor blade. If the algae are on a plant leaf, you may want to simply remove that leaf but scraping it off with a toothbrush may work.

7) Black Beard (or Brush) Algae

As you might have guessed from its name, this algae forms a dense mat of filaments that look like a brush or a beard. Like Staghorn algae, black beard algae grows on aquarium decorations, rocks, plants, and substrate.

Black beard algae holds on tight, so removing it with your finger or a toothbrush is challenging.

If practical, you may want to remove the item that the algae is growing on and give it a hydrogen peroxide bath, followed by a rinse in regular water to remove the algae.

8) Green Water

Green water is usually caused by tiny free floating algae in the genus Chlorella.

Tanks that are near windows that get natural sun light may experience Chlorella blooms because the algae seems especially attuned to sunlight.

Some aquarists actually try to create green water because it is thought to have health benefits for certain organisms like shrimp and even sick fish.

Pictures of Algae

If you want some detailed pictures to help you identify which algae is in your aquarium, check out Aquasabi’s article on algae.

Aquarium Algae Control

Controlling algae and removing algae are slightly different goals, and this article will talk about both.

You can think of controlling algae as the war, while removing algae is the immediate battle. There will be some overlap between the two, but focusing on algae control rather than immediate removal will lead to long-term success.

Algae Control Tips

1) Test Your Water

I know testing your water feels like a chore, but it can be really easy if you buy the aquarium water test strips only need to be dipped into the tank water for a couple seconds.

Yes, a complete aquarium water testing kit is more accurate but the test strips are more than adequate for figuring out if your water is loaded with nitrates.

Algae thrives off excess nutrients, and high levels of nitrates may be helping the algae spread quickly.

2) Increase Frequency of Water Changes

In natural ponds and lakes, rainwater refreshes aquatic environments by diluting and carrying away chemicals and nutrients like nitrates.

In a fish tank, that becomes your job.

Increasing how often you perform water changes will decrease nitrates and organic compounds, both of which fuel the growth of algae.

Also, if you feed your fish frequently or heavily, performing additional water changes will help keep your water at normal nutrient levels.

3) Add Plants or Add More Plants

Adding aquarium plants helps control algae because plants release chemicals that inhibit the growth of algae; it’s the way plants compete.

However, if excess nutrients or excess light are present, algae will typically get the upper hand over plants and cover the plants to the point that the plants cannot photosynthesize and die.

But if nutrients and light are in limited supply, plants will typically outcompete algae because they are able to store nutrients more efficiently.

If you need plants that can grow in low light conditions, get some Java Ferns and some Java moss; both will help you fight against algae.

4) Stock Your Tank with Algae Eaters

Fish like Otocinclus and Bristlenosed plecos devour algae. If your tank is small, stick with the Otocinclus as plecos tend to get pretty big.

Snails and Freshwater Aquarium shrimp, like Amano shrimp, are excellent algae eaters. In fact, only snails and cherry shrimp clean one of my tanks and it looks great!

5) Reduce Light

If your aquarium does not have live plants, reducing how long your light is on will help prevent algae growth.

If you leave your aquarium light on for 10 hours, try leaving it on for 4 to 5 hours.

If you have a planted tank, 6 to 8 hours of light a day is ideal for plants; any more than that and algae will begin to gain a photosynthetic advantage over the plants.

Ways to Remove Aquarium Algae from Plants and Décor

Starting with my least favorite method and ending with my most preferred way to remove algae:

5) 5% bleach solution (1 part bleach to 19 parts water): Hold or dip algae infested plant into the solution for 30 seconds (make sure to wear protection!). Then rise plants in regular water. Make sure not to dip the plant roots in the solution, only the infected leaves.

Works best for Black Beard Algae

Safe for fish? NO

I do not personally use the bleach dip method to remove algae from my plants because I prefer not to deal with something as toxic as bleach. Also, bleach is corrosive, so if it gets on anything, clothes, carpet, etc., it’s pretty much ruined. But here’s a video of how it’s done:

4) 3% Hydrogen Peroxide: Spray algae infected area with hydrogen peroxide.

Works best for Black Beard Algae

Safe for Fish? NO

I have seen videos of people spraying Hydrogen Peroxide directly into their aquarium.

I would do that, but I want my fish to live.

Instead, just remove the plant you want to treat and dip it into a Hydrogen peroxide bath. Then rinse the plant. I also do not personally use this method but at least peroxide is not as toxic as bleach.

But, if you want to try using hydrogen peroxide in your tank to remove algae, check out this video:

3) Scrub it away

The good old elbow grease method. Grab a toothbrush, sponge, or those fancy magnets and get to work scrubbing that glass. You can use your hands and fingers to remove algae from plant leaves.

Safe for fish? Yes, unless you are a maniac.

2) Get some Amano Shrimp

Amano shrimp are voracious algae eaters and will help you battle algae problems over the long term. These shrimp are not an instant solution, but they will eat algae and they are fun to watch.

Other freshwater shrimp species like cherry shrimp will also eat algae, but I find that Amano shrimp work a little harder to find algae.

1) Use Snails

I discovered this secret weapon by accident. People probably don’t mention snails because they are treated like the plague.

But, I bought some new aquarium plants and (of course) after a couple weeks my entire tank was covered in algae, the long stringy type. I mean my plants were covered in stringy green stuff and the foreground looked was covered in a fluffy shag carpet. I also noticed baby snails in my tank.

I then drained my tank and threw it in a dumpster. Just kidding! I actually just left it alone and to my amazement, my jaw literally dropped, the tank was spotless after about a week.

As soon as the snail army gained enough recruits, they demolished my algae problem.

Yes, not I have a snail problem, but I prefer that to an algae problem.

Seriously, get a couple Ramshorn or Nerite snails if you need to rid yourself of algae.

Snails are a safe, effective, and relatively quick solution for removing algae.

Snails will leave most of your plants alone too, but I have noticed that my Staurogyne repens is a little chewed up. But, the snails have not touched my Java ferns or Anubias plants.

Conclusion

The main takeaway about aquarium algae is shifting from an “eliminate it” mindset to a “control” or maintain it mindset.

Algae is a natural part of having an aquarium and it should not decrease the enjoyment of your tank.

Setting up systems for controlling algae, like increasing water changes and adding snails, is all part of the joys of maintaining a beautiful tank.

If you let yourself enjoy the process of caring for and tweaking variables in your aquarium, having one will become more of a delight rather than a chore.

Stay zen aquarists.

About The Author

Aquariums have been a passion of mine since the age of 7 and the nature aquariums created by aquascapers like Takashi Amano mesmerized me. But, I felt like I had neither the money nor the skill to create a stunning aquascape. So, I experimented with low-tech aquascapes, using low light plants and affordable equipment. And it worked! Now, I want to show other aquarists how they can create beautiful nature aquariums using basic equipment and hardy plants.

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