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?

Contrary to popular belief, algae are not evil. Algae, like plants, use photosynthesis to convert light and other nutrients (such as fish waste) into algae growth. That means they also produce oxygen during the daytime and 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 a neighbor who has a perfectly manicured lawn. Even the best-groomed lawns will occasionally get weeds (such as algae in an aquascape). These weeds must be addressed. Let’s say your lawn isn’t so nice and has five dandelion plants that are 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 is my fish tank so full of algae?

Algae is caused by an imbalance of nutrients and lighting in your aquarium. It is not easy to grasp this simple fact, but plants require just the right amount light and nutrients for optimal growth. The algae will thrive on too much light and not enough nutrients to build their cells. 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. It is almost impossible to achieve a balanced tank. Even if everything is in order, your plants will continue growing or you will trim them to change the nutrients and lighting.

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. This one-two punch strategy is very effective in reducing algae to negligible levels. In the following section, we’ll be discussing the six most common types of aquarium algae with targeted tactics of dealing with them.

Brown Diatom Algae

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. This algae is easy to remove, as long as you give it time. The plants will naturally consume excess phosphates or silicates. Clean-up crews also love it.

Brown algae

Black Beard Algae (BBA)

BBA is one the most troublesome algae because it is not eaten by many animals. 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. 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. Be aware that some plants, like the vallisneria plant, can be sensitive to liquid CO2.

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. The dying algae turns red or clear, and animals may eat it in its weakened state. 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). Because they grow quickly and are difficult to remove, these algae can become a problem. These algae are usually caused by too many nutrients (such iron), too little light or not enough nutrients (to match long lighting periods). 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. They can also be helped by brushing out large clumps manually 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. A lot of things can cause an outbreak, such as too much light or an imbalance of phosphate. Try using a glass-safe or acrylic-safe algae scraper (with the blade attachment) to remove the algae from aquarium walls.

Nerite snails are also a good first line of defense since they seem to like eating GSA. 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 technically not a type of algae, but rather a cyanobacteria that grows like a slimy blanket coating the substrate, plants, and decor. It comes with a rather distinctive smell that many fish keepers learn to recognize before the bacterial colony is even 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.

Bluegreen 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. 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. Repeat the treatment one more time for stubborn cases. For more information on treating BGA, read our full article here.

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. You can also buy a UV sterilizer that will kill all the algae within two-three days.

Green water

How to Balance Lighting and Nutrients

When it comes to fighting algae, everyone always assumes you must decrease lighting and/or nutrients, but sometimes the better course of action is to increase one or both of them. Let’s return to the example of a green lawn and five dandelions.

It is not sensible to stop watering your grass (e.g., stopping using fertilizers or lighting) in order to eliminate a few unwanted weeds. This will likely lead to your grass dying. 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.

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!