Aquarium Algae Types

Algae Buildup

There are quite a few different aquarium algae types that you may find develop in either your freshwater or saltwater tank. In this post, we’ll cover 8 common aquarium algae types to watch out for, and how to treat them if one or more of them occur in your aquarium. View our aquarium algae treatment and control page for products that can help remove algae.


1. Brown Algae (Diatoms)

Brown algae is a type of Diatom or microalgae, which is able to survive in lower lighting conditions. This algae initially forms as a dusting on the substrate in your aquarium. A few days later, it will have spread as a slimy film across the glass in your tank. Typical causes for brown algae growth include having insufficient lighting in your aquarium, high levels of silicates, nitrates, or phosphorus, and low levels of oxygen. It is common in new aquariums during the nitrogen cycle.

How to Remove Brown Algae

To remove brown algae from your aquarium, you will need to remove the nutrients it depends on to survive. Use a vacuum to remove the brown algae. Once finished, use a soft cloth to wipe down your aquarium glass. To remove the nutrients, do partial water changes. Also be sure to check your aquarium lighting to ensure you’re not using too little or too much light. Natural sunlight can also be a problem – ensure that light isn’t reflecting off any mirrors, white walls, or pictures in the room.

Pro-Tip: If water temperature is contributing to brown algae growth, be sure to lower the temperature in your tank gradually. Quick changes in temperature can shock your fish and invertebrates.


2. Black Beard Algae (Audouinella/Black Brush Algae/BBA)

Black beard algae is a type of red algae that typically appears in saltwater aquariums, however, it may also be found in freshwater tanks. This algae has a blackish or purplish appearance and grows in hair-like patches in your tank. This slippery algae is tricky to remove and looks a bit like a beard – hence its name. Low or varying CO2 conditions as well as inconsistent lighting are the leading reasons why black beard algae may start growing in your tank.

Another common cause is water flow. If your tank is experiencing a lack of oxygen, you can add an air pump to help improve oxygen levels. Also, be sure to check the temperature of your water. If it’s too warm, it will hold less oxygen.

Black Beard Algae - Algae Aquarium Types

How to Remove Black Beard Algae

Black algae can be removed manually by using an algae scraper. It can be notoriously difficult to remove, so that help, you can use Seachem Flourish Excel. Another option is to dip plants that are heavily covered by the algae into a 1:20 ratio bleach and water solution for approximately two to three minutes.

Pro Tip: Make sure that all your aquatic plants, hardscape items, etc. have no bleach on them prior to adding into the tank, and never pour bleach directly into your tank.


3. Blanket Weed (Cladophora sp.)

This is widely considered one of the worst, if not the worst of aquarium algae types to remove from your tank. Blanket weed (Cladophora) grows as a tough, green, mat or “blanket,” which forms on hair grass, substrate, and hardscape objects. The blanket weed is usually introduced into an aquarium via poor quality plants, such as Marimo Balls. Once introduced to the tank, this algae will grow and spread rapidly, particularly if you have high levels of CO2, nitrates, and light.

How to Remove Blanket Weed

Should you have a small infestation of blanket weed, you may be able to remove this pesky algae yourself. Upon removing, you’ll want to shut off the current in your tank to avoid unknowingly creating new populations of the algae during the removal process. When removing, use a pair of long tweezers and remove as much as possible. Then use Excel with a syringe to help remedy the worst areas where the algae tends to grow.

Pro Tip: Make sure you are choosy about WHERE you purchase your aquarium plants from to avoid this tricky algae. Always quarantine new aquatic plants before introducing them into your tank. It is best to avoid this algae at all costs because it is very tricky to completely remove.


4. Blue-Green Algae (BGA)

Technically, blue-green algae isn’t a true algae. It is classified as an aquatic cyanobacterium. It is a nitrogen-fixing bacteria, which means it will absorb all the nitrogen in your tank. Blue-green algae is an issue because it is a rapidly-growing cyanobacterium that quickly covers everything in your tank with either a green, blue, reddish-purple, or brown slimy substance. You’ll commonly find it along the front of your tank’s glass where it is hit most often by light. Common causes of the growth of blue-green algae include: high levels of waste from overfeeding or too few water changes. As your blue-green algae/cyanobacteria develops, it will use up your nitrates.

How to Remove Blue-Green Algae

The most effective way to remove blue-green algae from your tank is to use a technique called “Black Out.” BGA cannot survive without a source of light. There are other ways to remove blue-green algae such as 1.) doing a 50% water change, 2.) testing your nitrate levels to see if they’re too low, 3.) adding an airstone, 4.) turning off your lights for three to four days, and then 5.) testing the results after doing the first four steps to see if there’s a slowing of BGA growth. We recommend trying these options prior to performing a “Black Out.”

Pro-Tip: Use “Black Out” as a last resort to remove blue-green algae. Remove ALL sources of aquarium light or natural lighting that shine into the tank. During this process, you will need to keep your tank well-aerated. Your aquatic plants will handle the process of “Black-Out” better than the algae will. Feed your fish and other livestock sparingly (you can turn on lights briefly for this). If you have aquatic plants that rely heavily on light, keep the “Black-Out” up to a maximum of seven days. Your shade-preferring plants such as Anubias, Cryptocoryne, mosses, and ferns, will be fine for a two-week “Black-Out.”


5. Fuzz Algae

This short green algae creates a fuzzy appearance on your aquatic plants, aquascaping decor, and aquarium glass. It typically grows in new tanks, which are more subject to a nutrient imbalance because they are still maturing. If your tank is more mature and you have fuzz algae growing out of control, your aquarium is experiencing an imbalance of nutrients and low levels of CO2. A small amount of fuzz algae in your tank is fine.

Siamese Algae Eater - Aquarium Algae Types
Siamese Algae Eater

How to Remove Fuzz Algae

To help remedy your tank’s fuzz algae, first test the levels of nutrients and CO2 levels and adjust as needed for the proper balance. Then, you’ll want to invest in some algae eaters who will effectively remove your fuzz algae. These include: 1.) Siamese Algae Eaters (SAE), (pictured here) 2.) Amano shrimp, 3.) Otocinclus, 4.) Black Mollies, or 5.) Bristlenose Plecos. Investing in these critters and fish will help create a better aquatic environment for your plants to thrive in so that they will outgrow and no longer have to compete with the algae for nutrients.

Pro-Tip: We recommend first testing your nutrient and CO2 levels to see if that helps resolve the fuzz algae outbreak. If the issue persists, investing in algae-eating invertebrates and fish will help to remedy the problem, as well as prevent the algae from growing again in the future.


6. Green Aquarium Water Algae

If you suddenly experience aquarium water that turns a unsightly pea-soup green coloration, you likely have green aquarium water algae in your tank. Fortunately, this algae isn’t toxic to your fish. If grows when a bloom of unicellular algae occurs, replicating quickly and spreading around your tank. Typically, the causes of green aquarium water algae are either:

  1. a sudden amount of lighting, or
  2. a spike in the level of nutrients in your tank.

For example, a sudden amount of ammonia or a double dose of fertilizer will help to cause sudden green aquarium water algae growth. Another cause may be when you overfeed your fish and then forget to do a water change. This will result in an excess in nutrients, which also aids in the undesirable growth of green aquarium water algae. New tank owners should also ensure there’s plenty of nitrates that can take care of the ammonia levels to avoid any growth of this algae.

How to Remove Green Aquarium Water Algae

First, you’ll need to know that water changes do not effectively mitigate your green aquarium water algae issue. The reason? This algae is a single-celled organism. As a result, you’ll have to use a UV sterilizer or a “Black Out” technique. You can also invest in a couple algae eaters:

  1. snails
  2. shrimp

Pro-Tip: Please note, “Black-Out” is a last resort technique. We recommend utilizing a UV sterilizer and invertebrates first to remedy the growth of green aquarium water algae unless the issue continually persists.


UV Sterilizer Products


7. Green Dust Algae (GDA)

Green dust algae (GDA) is sometimes misidentified as Green spot algae, however they’re not the same type of algae. GDA is a surface clinger and will grow as a green slime on your aquarium glass, but not in your water.

This algae occurs commonly in new planted aquarium setups. Every now and then, it also occurs in mature aquariums that are experiencing an insufficient or erratic balance of nutrients and CO2. It isn’t harmful to your aquatic plants or your fish – it just looks bad.

How to Remove Green Dust Algae

First, ensure you have an aquarium test kit on hand. Be sure to test your levels of pH, phosphates, nitrates, etc. If there’s an imbalance, resolve it, and then, you can invest in a UV sterilizer if you don’t already have one. A UV sterilizer will kill the algae spores that are living in your water. You can also invest in Bristlenose Plecos who will eat your algae.

Pro-Tip: Possibly the most effective way to get rid of green dust algae in your aquarium is to do nothing and wait for the algae to complete its life cycle (which lasts for about 4 weeks).

Green Algae on Glass - Algae Aquarium Types

DON’T ATTEMPT TO REMOVE THE ALGAE DURING THIS PERIOD. Attempting to wipe away the green dust algae will cause the algae to release spores and start the life cycle over again. When the four weeks are up, perform a water change and lower the water level as much as you can. Then wipe the algae off the glass.


8. Green Spot Algae (GSA)

As we mentioned before, the similar-growing GSA, or green spot algae, looks like GDA and may also grow in your tank whenever there’s an imbalance of nutrients in your tank. This occurs when there’s not enough water changes, poor fertilization, or a lack of phosphates. Other potential causes include low CO2 levels, poor water flow, and exposing your tank to too much light. Green spot algae will look like patches of small green spots on your glass, equipment, decorations, and even plants.

How to Remove Green Spot Algae

Check your phosphate levels to see if they’re low. If so, be sure to treat that first. Once adjusted, you can remove the spot algae from the glass with an algae scraper. Be sure to check how long you’re leaving your aquarium lights on (around 9 hours is sufficient because prolonged lighting helps this algae to grow). Green spot algae eaters you can buy are sun snails and nerite snails.

Pro-Tip: If a lack of phosphates is the problem, we recommend using Seachem Flourish Phosphorus to help raise the levels of phosphates in your tank.


Flourish® Products

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SKU: SC2391
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SKU: SC2392

Aquarium Algae Types: Final Thoughts

You may have noticed a pattern in how to treat the various aquarium algae types. There isn’t one way to treat them all, however, common patterns include:

  1. overfeeding your fish,
  2. allowing too much or too little aquarium light (or natural light) into your tank,
  3. not performing enough water changes, and
  4. having an imbalance or too low of levels of CO2, nitrates, and phosphates.

Learn more about algae busters here.

New Tank Owner? Expect to See Some Algae!

Please bare in mind that several aquarium algae types will grow in new planted aquariums. In fact, you can expect to see “hair” algae or brownish-green diatoms in a new planted tank. For removing hair algae, turn the lights off for several days and don’t add any plant food to the tank. Then, siphon off dead algae. If you have brown or green diatoms, remove them from your glass and siphon or brush away from your rocks and decorations. Once your aquarium plants start growing, the diatoms should disappear.


Aquarium Algae Eaters

Purchasing a few cleanup crew invertebrates and fish such as Amano Shrimps, Rosy Barbs, Black Mollies, Otocinclus, and Bristlenose Plecos will also help, as they will happily feast on many aquarium algae types. Learn more about how to care for Amano shrimp, or follow the links below for reliable sources of livestock.

Questions? Please contact the experience team at SevenPorts. Our team are aquarium enthusiasts ourselves, and we can help point you in the right direction to help you mitigate your algae growth. We will also recommend the right products to boost the health of your plants or to help reduce or get rid of algae.

There are other aquarium algae types we didn’t cover in this blogpost, but we hope that this guide has been a helpful start to ensuring great plant health and a more clean-looking tank! Learn more about fighting algae one step at a time here.