How to Fight 6 Types of Algae in Your Fish Tank

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How to Fight 6 Types of Algae in Your Fish Tank

Do you dream of having a beautiful aquarium but end up constantly fighting to keep algae at bay? It’s a familiar struggle that many of us have been through, so in this article, let’s get a better understanding of the root causes of algae, the most common types found in freshwater aquariums, and how to gain the upper hand.


Algae is bad for fish tanks

Algae, contrary to popular belief is not evil. They use photosynthesis, which is similar to plants, to convert light and organic nutrients from water (such a fish waste) into new growth. They also produce oxygen in the daytime, and then consume it at night. Unlike plants, algae are a less complex lifeform and therefore can survive in “worse” conditions than plants, meaning they can absorb more wavelengths of light and consume different compounds that plants can’t use.

Algae is actually a good thing for your aquarium’s ecosystem because many fish and invertebrates like to eat it and it helps clean the water as a form of filtration. Plus, certain algae can look attractive and make an aquarium seem more natural. Most people dislike the appearance of these algae, especially in planted aquariums, as it can block out the view and scenery in a fish tank.

The reality is that there is no such thing as a perfect planted aquarium that is 100% free of algae. Imagine you have a neighbor with a well-groomed lawn of grass. Even they may get the odd weed, such as algae in an aquascape. This must be taken care of. Now let’s suppose your not-as-nice lawn has five dandelion weeds that have grown to one foot tall. The lawn will look like it has no weeds when you mow it. The same goes for algae control. We want to make sure you don’t see it, and that your tank looks spotless.

Why Does My Fish Tank Have So Much Algae?

Algae is caused by an imbalance of nutrients and lighting in your aquarium. This simple statement can be a little difficult to unpack, but basically, your plants need just the right amount of lighting and nutrients for optimal growth. Algae will multiply if you provide too much light but not enough nutrients. The algae will thrive on the extra nutrients you provide, even if there is not enough light. Light regulates how fast plants can absorb nutrients. A perfectly balanced tank is not possible. Your plants will grow and you will have to prune them.

How do I get rid of algae from my fish tank?

Since you will always have some imbalance between lighting and nutrients, the goal is to get your aquarium as close to being balanced as possible, and then use an algae-eating crew to fill in the rest of the gap. We have found this one-two punch strategy quite effective at greatly reducing algae to unnoticeable amounts. In the following section, we’ll be discussing the six most common types of aquarium algae with targeted tactics of dealing with them.

Algae Brown Diatom

Brown (and sometimes green) diatom looks like a dusty, flour-like substance covering your aquarium walls, substrate, and other surfaces. It’s soft enough to be rubbed off with an algae scrubber sponge. This is why many animals like shrimps, snails and catfish love it. Diatom algae is most commonly seen in newly planted tanks and is often caused by high levels of phosphates and silicates. Diatom algae is one of the easiest to eliminate. If you wait, it will consume excess phosphates.

Brown algae

Black Beard Algae (BBA)

BBA is a very problematic algae. It’s not easy to eat. It is a thick, bushy, clump-like algae that grows in dense, bushy clumps. They are often black or grey, but can also be reddish or brownish. This algae likes to grow on driftwood, aquarium decor, and plants, and if left unchecked, it can completely engulf an aquarium in one to two years. Unfortunately, there’s a lot of different things that can contribute the growth of BBA, detritus, so there’s no one simple way to treat it.

Black beard algae

You can add Siamese algae eaters or Florida flagfish to your aquarium to get rid of the ugly look. However, the shrimp will take longer to eat unless you have a large number. Some people turn to chemical treatments, such as using liquid carbon to directly spray on the BBA for tough cases or to dose the entire aquarium’s water column for mild cases. Just be careful because certain plants like vallisneria are sensitive to liquid carbon.

Another chemical treatment is to spray the BBA-infested plant or decor with 3% hydrogen peroxide (purchased from your local drugstore) outside of water, let it sit for 5 minutes, rinse off the chemical, and put the item back in the aquarium. Animals may eat the dying algae if it is still clear or red. Be aware that BBA cannot be removed quickly. It can take anywhere from six to eight to nine months for BBA to become established.

Hair Algae

In this category, we’re referring to the many types of algae that look like wet hair when you take them out of the aquarium (e.g., hair algae, staghorn algae, string algae, and thread algae). These algae can cause problems because they grow quickly or are difficult to eradicate. These algae are usually caused by too many nutrients (such iron), too little light or not enough nutrients (to match long lighting periods). You can reduce your lighting, increase fertilization, and decrease iron. Clean-up crew members include Siamese, molly, Florida flagfish, and amano shrimp. You can also help them by manually removing large clumps using a toothbrush.

Hair algae

Green Spot Algae (GSA)

GSA looks like tiny, hard green spots on the aquarium walls and slower growing plants that are very difficult to clean off. An outbreak can be caused by a variety of factors, including too much sunlight or an imbalance in phosphate. Try using a glass-safe or acrylic-safe algae scraper (with the blade attachment) to remove the algae from aquarium walls.

Because they like GSA, Nerite snails can be a good first defense. Just be aware that, while this species does not reproduce in freshwater aquariums, they will lay white eggs (similar to little sesame seeds) all over the aquarium, and some people don’t like the look.

Nerite snail eating green spot algae

Blue-Green Algae

BGA is not technically an algae type, but a cyanobacteria. It grows as a slimy coating on substrate, plants and decorations. Many fish keepers are able to identify the distinctive smell before the bacterial colony becomes visible. No one is 100% sure what causes BGA, but in general, improved aquarium upkeep and increased water circulation with an air stone or powerhead can help keep it away. Algae eaters typically will not eat the stuff, so don’t count on their help in this case.

Blue green algae or cyanobacteria

BGA can be photosynthetic and you may want to blackout your tank for one week. This can be difficult on plants. We recommend that you manually remove as much BGA as possible. Next, water changes should be made while vacuuming the substrate. The tank will then be treated with antibiotics. Use one packet of Maracyn (which is made of an antibiotic called erythromycin) per 10 gallons of water, and let the aquarium sit for one week before doing another water change. For stubborn cases, repeat the treatment one additional time. Read our complete article to learn more about treating BGA.

Green Water

If your aquarium water looks like pea soup, you probably have green water, which is caused by a proliferation of free-floating, single-celled phytoplankton. These phytoplankton can multiply so fast that it is difficult to flush them out with large water changes. You can get green water from too much sunlight (especially when the tank is in direct sunlight during the day), excessive nutrients (such a accidentally double-dosing fertilizers), and an ammonia surge (such a new tank or overfeeding from a pet sitter). To get rid of green water, you can blackout the tank for at least a week, which is hard on your plants. Another option is to purchase a UV sterilizer, which will kill off the algae within two to three days.

Green water

How to Balance Lighting and Nutrients

Everyone assumes that you need to reduce lighting and/or nutrients to fight algae. But sometimes it is better to increase either one or both. Let’s take our example, where we have a green lawn with five dandelions.

It’s not a good idea to stop watering your lawn (e.g. stop using fertilizers and lighting) to remove a few weeds. You’ll likely end up killing your grass. Instead, we remove the weeds manually or use a snail for their removal. We also feed the lawn more to make it healthier so they don’t return as often.

It is important to focus on the growth of many plants and not on eliminating any algae. To balance the aquarium, put your light on an outlet timer as a constant factor, and then gradually increase or decrease your nutrient levels with an all-in-one fertilizer. Do not make multiple or drastic changes all at once because it takes at least two to three weeks to see any difference in your plants and determine whether or not your actions helped balance the aquarium. For more information on how to troubleshoot your aquarium, please refer to our article on plant nutrient deficiencies.

The Internet claims that if you do everything perfectly, your tank will never get algae, but in our experience, this is highly unlikely in the real world. The use of the algae-eating shrimp amano was popularized by Takashi Amano (the father of modern aquascaping). So, don’t be afraid to bring in the right algae eaters to help out while you’re trying to fix your lighting and nutrient balance issues. Best of luck on your plant-keeping journey!