How to Fight 6 Types of Algae in Your Fish Tank

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.

Are Algae Bad For Fish Tanks?

Algae, contrary to popular belief is not evil. Like plants, they use photosynthesis to convert light and organic nutrients in the water (such as fish waste) into new algae growth. This means that they can also produce oxygen during daylight and consume it at nights. Algae are less complex than plants and can live in harsher environments than plants. They can absorb more light wavelengths and consume compounds that plants cannot.

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 a neighbor who has a perfectly manicured lawn. Even they will get the occasional weed (like algae in an aquascape) that must be dealt with. Now let’s suppose your not-as-nice lawn has five dandelion weeds that have grown to one foot tall. If you mow the lawn, then it will appear as if you have no weeds. We want to know how to control algae in a way that is invisible and leaves the tank looking clean.

Why is my fish tank so full of 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. Algae will benefit from the additional nutrients if you give them too much nutrients and not enough light. This regulates the speed at which plants can use the 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 in 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 is so soft that it can be easily scrubbed off with an algae sponge sponge. Many animals, including shrimp, snails, and catfish, love to eat it. High levels of silicates and phosphates are often the cause of diatom algae, which is more common in tanks that have just been planted. It’s one of the simplest algae to get rid of because if you just give it some time, the plants will naturally consume the excess phosphates and silicates, and clean-up crews love to feed on it.

Algae with brown color

Black Beard Algae

BBA is one the most troublesome algae because it is not eaten by many animals. As per its name, it grows in very thick, bushy clumps that are usually black or grey in color (but sometimes 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. BBA can grow on many different things, so there is no single treatment.

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. Some plants, such as 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. Just remember that there are no quick fixes – BBA can take six to eight months to get established, so expect it to take at least that long to get rid of.

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 can be caused by an excess of nutrients (such as iron), too light, or a lack of nutrients (to meet the long lighting time). Therefore, try decreasing your lighting period, increasing fertilization, or decreasing iron. Siamese algae eaters, amano shrimp, molly fish, and Florida flagfish are good candidates to use as clean-up crew. You can also manually remove large clumps with 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. Too much light or an insufficient amount of phosphate can lead to an outbreak. 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)

BGA is technically not an alga, but is a cyanobacteria. This cyanobacteria grows like a thin blanket covering the substrate, plants, decor, and other elements. 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-eating algae won’t usually eat it so don’t count on them to help.

Blue green algae or cyanobacteria

Since BGA is photosynthetic, you can try to blackout the tank for a week, but this can be hard on the plants. Instead, we recommend manually removing as many BGA as you can, performing a water change, vacuuming the substrate, then treating the tank using 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. Unfortunately, they replicate so quickly that you cannot flush them out with large water changes. Too much light (especially during the day), excess nutrients (such accidentally double-dosing fertilisers), and ammonia spikes (such as a new tank not cycled yet, or pet sitting). 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 go back to our example where you have a green lawn with five dandelions.

It doesn’t make sense to stop watering your lawn (e.g., stop using lighting and fertilizers) just to get rid of a few weeds because you’ll probably end up killing your grass too. Instead, we pull out the weeds (e.g., manual removal of the algae, or get a snail to eat them), and/or feed the lawn more often so it is healthier and won’t be as susceptible to the weeds coming back.

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.

Although the Internet says that algae will not grow in your tank if everything is done correctly, we have found this to be highly unlikely in reality. The use of the algae-eating shrimp amano was popularized by Takashi Amano (the father of modern aquascaping). You don’t have to be afraid to get the right algae eaters for your lighting and nutrient-balance problems. We wish you all the best in your plant-keeping adventure!