Controlling & Removing Beard Algae | Aquarium | Causes & Solutions | Tips
How to Control and Remove Beard Algae (Red Algae) in Your Aquarium—Tips from a Pro
If you spot dark green, black, or dark gray algae in your aquarium, good advice is hard to come by. That’s because these red algae are master survivors—they’re “here to stay.” In this guide, we’ll explain how to identify beard algae specifically, how to get rid of this stubborn type of algae—and how best to prevent it from entering your aquarium in the first place.
Identifying Beard Algae/Red Algae
They’re dark green, gray, or black, form strands up to 15 cm long that curl as they grow, and like to float in the filter’s current—what kind of algae is this? Most likely, beard algae have colonized your aquarium. This type of algae, along with brush algae, belongs to the group of red algae (Compsopogon)—which, however, don’t look red at all, but rather dark green to black.
Beard algae in the aquarium are often confused with thread algae. Thread algae, on the other hand, belong to the large group of green algae and are much easier to get rid of.
| Distinguishing Features | Differentiating | Algae type |
| Long filaments | curly, the longer they are | Beard algae |
| smooth, the longer | Filamentous algae | |
| easily detachable | Filamentous algae | |
| hard, cannot be removed | Beard algae | |
| more than 15 cm long | Thread algae | |
| short, tassel-like | Brush algae | |
| Color | bright, rich green | Thread algae (or young beard algae) |
| dark green to dark gray | Beard algae | |
| Alcohol test | does not change color | Filamentous algae |
| turns red | Beard algae/brush algae |
Beard algae, like all red algae, are very persistent. You’ll find them mainly on the edges of aquatic plant leaves or on hardscape and equipment—but especially in areas with plenty of oxygen, i.e., preferably in the current. The plant attaches itself to the substrate with extremely firmly adhering basal cells, and even if you thoroughly tear off the algae filaments, basal cells always remain, from which the algae will regrow.
If you try to remove beard algae from the aquarium, you’ll notice that the strands feel relatively firm. This is due to a unique mechanism of red algae: When the carbon dioxide content in the water drops, the red algae utilize the principle of biogenic decalcification. It uses the carbonate hardness of the water to extract calcium carbonate and CO₂ from the water to meet its high demand. This not only gives it a competitive advantage over higher aquatic plants, whose growth is stunted by the lack of carbon dioxide,
but the accumulation of calcium carbonate also makes the algae harder and more robust. Most algae-eaters steer clear of beard algae and their relatives, the brush algae, because they don’t taste good. So this trick for controlling algae in the aquarium hardly works on beard algae—unless you use our secret trick. More on that below!
Causes of beard algae in the aquarium: How to prevent it
image source: coffmancmu ( #270140108) - Adobe Stock
If you spot algae in your aquarium, it’s usually a sign that something is wrong with the nutrient balance. There are many possible causes for an out-of-balance system: a change in environmental conditions—such as more sunlight or a new fluorescent tube—a different type of fish food, a decline in filter performance, or an overdue water change can all lead to algae finding a niche that they’ll occupy in the blink of an eye.
In all likelihood, beard algae are already present in your aquarium without you even noticing them. It’s virtually impossible to have an algae-free aquarium. The tiny algae spores travel from the pet store, in fish food, or simply through the air, and they’re unstoppable. But here’s what you can do: create conditions that make it difficult for algae to multiply. You can prevent these common causes of beard algae in your aquarium—or at least remedy them afterward:
| Problem | Description | Solution |
| Too little carbon dioxide in the water | Aquarium plants grow more slowly, which makes it easier for beard algae to spread; biogenic decalcification produces a hard algae skeleton and makes beard algae unattractive to algae-eaters | Frequent water changes ; use a CO2 system |
| Too much oxygen / water flow | This isn’t a problem in itself, but beard algae thrive in strong currents. | Do not set the pump too high, do not choose a filter that is too large, and place the outlet deeper underwater |
| Insufficient planting / slow-growing plants | Not enough competition for beard algae, which allows them to multiply more quickly | Add more fast-growing plants; use carbon fertilizers for plants (EasyCarbo or Happy Carbo) |
| Certain plant species in the aquarium | Beard algae preferentially infests certain plant species: If Vallisneria, water primrose, and water star are present, these will be infested first. | Create a varied plant mix so that infested plants can be removed more easily |
| Excess nitrate | Algae love nitrate; along with phosphate, it is their most important food source and is often present in excessively high concentrations (even in tap water) | Conduct a nitrate test (in both the aquarium water and tap water); lower nitrate levels by feeding fish less and removing debris from the |
| Excess phosphate | Algae love phosphate; along with nitrate, it is their most important food source | Test for phosphate; reduce phosphate levels by removing activated carbon from the filter, downsizing the filter, feeding fish less, and thoroughly rinsing frozen food before feeding |
| General nutrient excess | If there are more nutrients in the tank than the aquatic plants need, algae will thrive | Measure water parameters (especially nitrate, phosphate, and iron); reduce the nutrient surplus by feeding/fertilizing less, performing frequent water changes, and shortening the lighting duration |
| Nutrient deficiency | If there are too few nutrients in the tank, this harms the aquarium plants and creates a niche for algae | Measure water parameters; stimulate plant growth with carbon fertilizer or liquid fertilizer |
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Measures Against Beard Algae in the Aquarium
There are plenty of tips, advice, and obscure methods circulating among aquarists for combating beard algae. Unlike harmless diatoms or many species of green algae, beard algae are very persistent and often difficult to remove. Be patient and try the recommended methods one after another to see what works. You should proceed step by step, gradually increasing the intensity of your efforts: Only when natural remedies have failed and adjusting the basic conditions hasn’t helped should you try chemical algae treatments. There’s always a risk that while the treatment kills the beard algae, it may also harm the other inhabitants of the aquarium. In the worst-case scenario, all your fish or aquatic plants will die within a few weeks, and the beard algae will still be there.
It’s not for nothing that experts recommend completely setting up an aquarium from scratch in cases of severe beard algae infestation—with new substrate, thoroughly cleaned equipment, and new aquatic plants.
Removing beard algae by hand
If you discover beard algae in your aquarium, the first step in combating it is to remove all visible strands as thoroughly as possible. This is best done by hand; beard algae aren’t as slippery as, for example, thread algae, and are easy to grip. Since the extremely firmly attached basal cells cannot be torn off during this process, you have two options, depending on where the beard algae have taken hold:
- You should remove beard algae from decorative items and equipment by taking the items out of the tank, scrubbing them thoroughly, and (if possible) boiling them. Items you can’t boil (e.g., decorative roots) should be wrapped while damp in a thick layer of table salt, which will draw the moisture out of the beard algae.
- For aquatic plants, it’s best to cut off the entire infested leaf; if the entire plant is affected, the only solution is to discard it.
Natural Remedies for Beard Algae
The most important measure against the spread of beard algae in the aquarium is to keep the algae in check. This is achieved primarily by fast-growing stem plants, which deprive the beard algae of nutrients and block light from reaching the water. If your aquarium has too few plants or if the plants are withering due to a lack of nutrients, this opens the door for beard algae. So make sure your aquarium is well-stocked with plants such as hornwort, waterweed, or hornwort to combat beard algae.
It is sometimes reported that lowering the pH level in the tank is an effective way to combat beard algae. This is achieved by adding humic acid, which gives the water a slightly brownish tint. Humic acid is formed through the bacterial decomposition of mulm in the substrate, but it can also be produced by using peat. To do this, peat pellets are placed in a small bag and hung in the aquarium; they should be replaced regularly until the algae have disappeared. Of course, you’ll need to make sure your fish can tolerate the lower pH level. We’re reluctant to recommend peat for aquariums because it’s extracted from bogs, which we urgently need to preserve in the fight against climate change.
Image source: Hippocampus
Another completely natural method for controlling beard algae is to introduce predators: shrimp, Siamese barb, or trumpet snails will devour beard algae root and all, as long as the algae haven’t yet accumulated too much calcium carbonate. Using a CO₂ system quickly softens the beard algae, and you can watch as they get nibbled away.
Note: If you introduce algae-eaters into your aquarium, you’ll need to decide: Should these fish be added only for the duration of the algae control and then transferred to another tank afterward? If not, they must be integrated into the current fish population. An overly dense fish population is, in fact, a trigger for algae outbreaks in and of itself. You should
also keep in mind that many algae-eaters only do their job as juveniles; afterward, they switch to other food sources. Think about what you’ll feed the algae-eaters once they’ve eaten all the algae in the aquarium.
Chemical Treatments for Beard Algae
Even experienced aquarists often reach the end of their rope when battling extremely stubborn beard algae. At that point, resorting to chemical treatments seems to be the only solution. Our product line includes various algae control products; however, based on our years of experience, these aren’t always effective against beard algae. So don’t expect miracles here.
One fairly reliable product is high-dose carbon (often referred to by the product name EasyCarbo), which you can use to give your aquatic plants a growth boost. Carbon fertilization can help them gain a decisive advantage in the race against beard algae and potentially displace them. However, this will only work if the algae infestation hasn’t yet gotten completely out of hand.
We specifically recommend the tried-and-true product Microbe Lift Algaway for combating beard algae. It works with a combination of salicylic acid and copper sulfate pentahydrate. You should always use these substances with great caution: Regular partial water changes of about 30% accelerate the effectiveness of the anti-algae treatment and ensure that the biocidal active ingredients do not harm your fish.
A last-resort treatment for beard algae is hydrogen peroxide. This chemical is extremely aggressive. When treating algae with it, it’s best to apply it locally by spraying the affected areas underwater using a disposable syringe. You should turn off the filter pump for a while so that the hydrogen peroxide remains in place. Sensitive fish must not come into contact with the active ingredient—it can literally burn their gills and scales. Germs often settle on the damaged areas, leading to the death of the fish weeks later. As a last resort, however, the misting method is often quite successful against beard algae. You’ll need to repeat the treatment daily until the algae turn pink or white—then you’ve succeeded.
Summary
When beard algae appear in the aquarium, good advice is hard to come by. These algae, which belong to the red algae family, form long, dense, curly “beards” over time and are often mistaken for thread algae. Unfortunately, beard algae are very stubborn. Instead of going to great lengths to combat and remove them, your best bet is to effectively prevent beard algae. The most important factor for this is a well-established tank with a balanced nutrient level, one that receives no direct sunlight, is densely planted with aquatic plants, and houses a balanced fish population that includes species that enjoy eating algae as a snack. If a beard algae infestation does occur, you should first check and stabilize the most important water parameters step by step and remove the visible beard algae by hand. Only when natural remedies against beard algae have proven ineffective should you resort to chemical treatments.
