Bryopsis Algae – A Cure

Bryopsis algae. Classified as macroalgae, B. pennata and B. plumosa, as it’s formally called, is quite difficult to properly identify and eradicate from your aquarium.

What is Bryopsis Algae?

At first glance, Bryopsis looks like small patches of underwater grass. In reef tanks, at the start of your outbreak, it is very small. In most cases, you’ll notice thin hair-like strands attached to live rocks or coral. Eventually, these few strands multiply like crazy into thick patches.

Officially classified as a photosynthetic organism in the bryopsidaceae algae family, Bryopsis proliferation is often triggered by water chemistry and light exposure. Are you wondering what causes Bryopsis? Well, you’re not alone, we will discuss this shortly. However, before diving into the cause of this frustrating situation, are you sure the algae overtaking your aquarium is, in fact, Bryopsis?

How to Identify Bryopsis

Identifying Bryopsis algae isn’t as easy as you may think. Sure, noticing an algae bloom is quite easy. Simply look for growing patches of what appears to be grass. However, just because it looks like Bryopsis, doesn’t mean it is.

More often than not, Bryopsis is mistaken for green hair algae (GHA). While it may look similar, there are several distinct differences between Bryopsis and hair algae. The most noticeable difference is its size. Bryopsis algae tend to be larger, both horizontally and vertically, than GHA, which often features shorter reach.

Next, look at the algae root structure.

Bryopsis algae roots itself deep into the surface of rocks or coral and forms a complex covering, which looks like a dense welcome mat. This provides Bryopsis with a sturdy grip to whatever surface it attaches to.

GHA, on the other hand, generally doesn’t have an easily identified root structure. It’s easily moved off rocks and can also grow in aquarium sand.

The branches of Bryopsis are distinct in comparison to any other green hair algae species. Essentially, the tiny hair-like strands resemble common variety ferns and feature dense trunks. GHA strands are smoother and have less-distinct physical characteristics.

Lastly, if you’re still unsure of algae type, turn to your tank inhabitants. The majority of creatures that enjoy an algae meal shy away from consuming Bryopsis. However, most members of your aquarium cleanup crew eat GHA without hesitation.

Two way of bringing Bryopsis into your aquarium

  • Live Rocks – Are considered an essential component for any marine tank, live rocks will boost your tank viability, but it’s not without some risk. Even the most cautious of aquarists can accidentally introduce Bryopsis into their tank via live rocks. Algae can attach to the surface of live rocks, you take it home add it to your aquascape only to find in a few weeks bryopsis has overtaken your aquarium.**
  • Coral, Coral Frag Plugs – Another very common cause of Bryopsis infestations occurs when corals and coral frag plugs are placed into your display tank. If you do not really know the person you purchased your coral or frag from do not put it in the tank with your existing corals.**

** I always recommend to aquarists; quarantine new items prior to adding to your display tank. Unless you are very confident in your LFS sales person, supplier or who you buy live hard goods (rock, coral, frags etc.) If unsure, I would recommend the use of dry rocks and a quarantine tank.

The rate of growth depends on many factors. Everything from light concentration to water parameters can either influence or hinders Bryopsis growth. However, a swiftly developing algae bloom is typically an indicator of higher-than-desirable phosphates and nitrates.

This is where the bryopsis begins its stealthy attack in your tank. Way before you see the large patches overtake corals & rocks, the elevated nitrates and phosphate levels generally aren’t detected with tests. As the Bryopsis population slowly expands, its consumption of nitrates and phosphates gives the illusion that your tank water parameters are correct.

The bryopsis attempts to hide until its population as it grows in size and number. Once this happens, removing this invasive algae is far more difficult.

Bryopsis Reproduction and Life Cycle.

As an asexual macroalgae, Bryopsis algae accelerates reproduction through fragmentation. Meaning, the entire colony self-replicates by releasing cells out into the moving water.

This is how an unnoticed patch of bryopsis algae on a piece of live rock or coral or frag can result in complete tank domination.

While asexual reproduction occurs naturally, you can actually increase its spread. When you notice the green filaments on a piece of rock or coral, you quickly reach in to remove the algae however, small bits will have flaked off during the rubbing, scratching or pulling of filaments.


Only a few cells are required to repopulate this particular species, you may think you have won, though now things are going to really heat up.

REMEMBER: Do not pluck, pick, scratch or rub at the Bryopsis. Now you ask, how do you kill Bryopsis? One word: sneakily.

How to Remove Bryopsis Algae.

There’s a reason why marine aquarists loathe this alga more than almost any other invasive problem. The reason is that Bryopsis is a serious pain to remove.

When you think you’ve finally beaten it, it reappears. Sitting on your favourite coral, frag or rock, the filaments wave at you, and you feel defeated.

Just because it’s difficult to kill doesn’t mean it’s impossible.

Best Way to Get Rid of Bryopsis in Your Aquarium

Bryopsis can be a thorn in the side of many aquarium hobbyists. If you’ve been unfortunate enough to encounter it, you’ll know it’s something you’d rather avoid. Here’s a guide on both prevention and treatment of Bryopsis.

Prevention: The Role of a Quarantine Tank

  • Often called a ‘hospital tank’, a quarantine tank is a backup to house your fish and coral if Bryopsis takes hold in your main setup.
  • Should Bryopsis appear, simply move your fish and coral to the quarantine tank. This allows you to thoroughly treat or even restart your primary tank without causing harm to its inhabitants.
  • Once your main tank is clear and safe, you can reintroduce your fish and coral.

Treatment for Bryopsis For those without the luxury of a quarantine tank:

  1. Enlist Fishy Help: Certain fish are natural predators of Bryopsis and can aid in its control. Examples include:

    • Rabbitfish, Lettuce nudibranchs, Longspined urchin, and sea hare.
    • Parrotfishes, such as Siganus vulpinus and Z. xanthurus.
    • Tangs, like Kole tangs, Orange shoulders, Halfblack, and Bristletooth tangs.
  2. Adjust Magnesium Levels: Elevate the magnesium in your tank to +1500 ppm. Utilize a blend of magnesium sulfate and magnesium chloride supplements.

Things to Avoid

  • Do Not Pull Out Bryopsis Directly: This action disperses spores and can exacerbate the spread.

General Tip for Marine Tanks:

  • Regulate Nutrients: Lessen the nutrient input by moderating food amounts, thereby reducing the bio-load. Additionally, incorporate Macroalgae to further eliminate excess nutrients.

Will Anything Eat Bryopsis?

Unfortunately no, Bryopsis is not liked as a food source (some may nibble at it, though nothing to note).

Fluconazole Treatment

Fluconazole, traditionally used as an antibacterial medicine for a various fish diseases, aquarists worldwide have uncovered a unique use of Fluconazole. 

According to a variety of reports, aquarists are successfully killing Bryopsis algae with this medicine. Bryopsis Buster is an aquarium Fluconazole treatment against fish fungal infections; the active ingredient is “Fluconazole”. Until I thoroughly researched its potential, I was extremely sceptical. However, the way it works makes it relative safety for other tank inhabitants this changed my thoughts about using it as a treatment.

If you are curious about this treatment method, there are several things you must consider. The first is to understand how Fluconazole kills Bryopsis.

Basically this medicine essentially dissolves the metabolic pathways responsible for cellular health. After a relatively short treatment duration the exposure to Fluconazole the Bryopsis cell walls or membranes stability is compromised which results in death.

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