Bryopsis Algae – These Methods Will Win The Battle!

After you have been in this hobby long enough there are times when algae will suddenly pop up in your aquarium. No matter how diligent you are about inspecting what goes into your aquarium, this junk still appears.

Hopefully, you don’t have too many algae appear, but I’m sorry to say you may get them all over the life of your aquarium! So far I’ve had almost everyone at some point! Its a pain in the rear, but knowing how to deal with it is key!

Bryopsis Algae is a very stubborn fern-like alga that can plague a saltwater aquarium. Common methods of eradication are maintained high Magnesium levels with Kent Tech-M Magnesium, Fluconazole, Hydrogen Peroxide, and Vibrant Aquarium Cleaner.

This article is how I treated my Bryopsis over 8 years ago, and since then there are some new products that are getting great reviews, so I’ve researched and added them in here too so you have ALL the options which have proven to work – It’s just hit or miss which one will work for you!

What Is Bryopsis Algae?

Bryopsis is an algae that belongs to the Family of Bryopsidaceae and within the Genus of Bryopsis, there are 138 different species. You can find more information Here at Wikipedia or Here at

The 2 species that are most common in our aquariums are:

  • Bryopsis pennata
  • Bryopsis plumosa

But you could find yourself facing one of the other species. It does not matter so much with species you have as the eradication ways we discuss should combat the whole Family of Bryopsidaceae.

How Do You Identify Bryopsis Algae?

Bryopsis in our aquariums is characteristically given away by its Fern-Like appearance. It can start really small but it can soon spread and if left untouched you can easily have an infestation, especially if your water has high Nitrates and or Phosphates!

A Small Clump Of Bryopsis
Bryopsis Infestation – Image Source

How Do You Get Bryopsis Algae In Your Aquarium?

The two main ways that Bryopsis, and pretty much most algae enters your aquarium are Live Rock and Frag Plugs.

Live Rock

When purchasing Live Rock for your aquarium or you are receiving a piece to help seed your Dry Rock then you really need to closely inspect every piece. This can be a very difficult task but the easiest way is to do it while the rock is underwater as all algae flops over and looks the same when the rock is out of the water.

If you are buying the rock at a local store have a really good look at the rock holding tanks and if you see ANY pests or nuisance algae in it just walk away and go somewhere else. The battles you could face are not worth the cheaper rock!

Frag Plugs

This is by far the most common transportation method for nuisance algae and living pests to enter your aquarium. Very careful inspection of every frag plug you intend to put in your aquarium is needed.

If you can, remove the coral frag and glue it to a brand new plug, then dip the coral. If the coral has encrusted over the plug then scrape as much of the plug as you can with a scalpel blade to remove any possible living spores, then dip.

Non-Encrusted Coral Frag
Encrusted Coral Frags

For a more in-depth look at coral dipping see the ‘Further Reading” section at the end of this article.

Are There Ways To Eliminate Bryopsis Algae?

Some ways involve some manual labor, some ways are a chemical approach and some ways are a bacterial approach. These are really the only ways to fight Bryopsis, unless you are one of the VERY lucky ones who has a fish that eats it, but if that’s the case you probably never knew you had Bryopsis in the first place!

Manual Removal

No matter how much Bryopsis you have, the fastest way to get rid of the majority is manual removal. Pick out as much of it as you can to help thin out the herd and then this will allow one of the other methods to work better.

The more algae that is present, the more plant there is to eliminate, thus diluting the removal powers of the substance. If you have fewer algae material in the tank for the same dosage, the treatment will work far better.

High Magnesium Using Kent Tech-M Magnesium

This was the only method that worked for me all those years ago. It was slow, but with patience it worked.

“Yep its not fun to deal with and if untreated it will own your system eventually. Here is one for you. Mostly all plants (Bryopsis included) have an affinity to bind up and absorb metals, actually metals are essential for the metabolisms of plants.
The problem is that when plants threshold limits have been reached in terms of metals, the metals become an enzyme inhibitor and enzyme inhibitors, in the case of Bryopsis, is just what we are looking for.
So, the plan is to stuff that plant with as much metal as we can so it reaches its threshold. Ok, ok, metals and corals are not such a good plan…but there is an exception…our buddy, Magnesium.”

Mike O’Brien (Mojofeef) – Reef Central Forum

Here is the common dosing process:

  • Raise the Magnesium level in your water to over 1600ppm and then keep it at this level for at least several weeks until all the Bryopsis has gone
  • Raise the Magnesium by no more than 100ppm each day
  • Each time you do a water change re-dose to maintain Magnesium level above 1600ppm

To work out how much to dose based on your total aquarium volume you can use this handy calculator:
Reef Chemistry Calculator By JDieck

Things To Consider When Using Kent Tech-M:

  • Do not exceed 2000ppm
  • Do not add livestock while treating for Bryopsis
  • Remove poly filter material – known to absorb elements within Tech-M formula
  • Test regularly using quality test kits like Elos, Red Sea or Salifert
  • If the test is off the scale – dilute with 50% RO/DI water and half the reading
  • Ensure you have enough Kent Tech-M to last possibly 6 weeks
  • Continue water changes as normal but re-dose to replenish Magnesium to maintain >1600ppm
  • Monitor Specific Gravity (Salinity) closely
  • Once Bryopsis has gone continue water changes without dosing until Magnesium is back at your normal level – 1250-1350ppm
  • Use treatment at your own risk – Process is not endorsed by Kent Marine

For whatever reason, this method ONLY seems to work with the Kent Tech-M Magnesium product. No one knows why and Kent will not divulge its ingredients but there is something in their Magnesium that works.

Myself and many others tried to take the cheaper road and use the bulk Magnesium granules we regularly use, but it never worked. Only when switching to Tech-M did the Byropsis receed.

There are rumors that Kent recently changed its formula for Tech-M Magnesium and aquarists are more Hit or Miss for it working in their aquariums. Something to think about, but they are rumors!

Here is a helpful article about using Kent Tech-M Magnesium to eradicate Bryopsis on the forum.


Fluconazole is a treatment intended for fish infections and diseases but it has been found to be a great treatment for the eradication of Bryopsis.

I could go into all the details here but there is an absolutely incredible, in-depth article with day-by-day photos and Q&A by NCReefguy over on the Reef2Reef forum about how he used Fluconazole to beat his Bryopsis infestation.
Click Here to see it.

Fluconazole works by blocking the cellular paths within the cells of the Bryopsis plant.

By blocking these paths, it impedes the distribution of a sterol that is similar to Cholesterol in humans. Without this sterol, the cell walls break down and the plant dies.

Two well-reviewed & popular Fluconazole treatments are:

Reef Flux
Available Here At

Flux RX
Available Here At

Things To Consider When Using Fluconazole:

  • Fluconazole will attack the cells of Macroalgae so any Refugium/Cheato must be removed before treatment.
  • Discontinue using Activated Carbon for 72 hours
  • Discontinue using any Phosphate remover for 72 hours
  • Turn down Protein Skimmer and remove collection cup

Depending on the brand of Fluconazole you use for treatment and the size of infestation you should see results within 1-2 weeks of starting the treatment. Be sure to follow each individual manufacturer’s instructions.

For some really good information on how the eradication of Bryposis using Fluconazole was first found, please see this forum on Reef2Reef where Jose Mayo, MD from Brazil talks about his research and findings.
Click Here To See It

Hydrogen Peroxide

The underdog of fixing many problems that most people never know about. Hydrogen Peroxide is a true giant of the things it can do and one of those is beating Bryopsis in our aquariums.

The only drawback with this method is for it to truly work you need to be able to remove the infested rock from your aquarium. This can be a quick, cheap fix if you have a nano aquarium or a smaller aquarium with a minimalist aquascape.

For those of you with large aquascapes or rocks cemented together this treatment is probably one to skip.

To treat Bryopsis using Hydrogen Peroxide here is a good procedure:

  • Remove the rock and place it into a clean bucket
  • Use a blade of some form to scrape off the Byropsis – Get as much as you can into the bucket.
  • Use a syringe full of undiluted 3% Hydrogen Peroxide and spot treat all the areas.
  • Leave it to soak for 3-4 minutes
  • Rinse the rock in some clean saltwater
  • Place the rock back into the aquarium
  • Repeat with other rocks as needed

If you catch it early enough this may be the only time you have to treat using this method. Many aquarists used to treat the whole tank to Hydrogen Peroxide but it could be harsh on your Coralline Algae and coral.

The new products on the market like Flucozane and Vibrant would be my recommendation if treating the single rock did not work.

Vibrant Aquarium Cleaner

Many aquarists seem to be getting very good results from a fairly new product called Vibrant Aquarium Cleaner by Underwater Creations.

Vibrant uses multiple strains of bacteria to attack the algae from different angles. One of the bacteria strains targets the Nitrates and Phosphates that feed your algae and turn them into biomass to be removed via your Protein Skimmer or water changes.

This product is also designed to work on any problem algae, according to the manufacturer.

You can read the forum thread HERE on Reef2Reef where Jeff the owner comes on and joins in the conversation regarding it! – Cool!

“Vibrant is a true beast and we have not yet come across a algae that Vibrant can not beat out. Below I will list a general timeline of how fast Vibrant works on frequent algae strains that cause issues in reef aquariums”.

Cloudy/hazy Water– 1 dose
Diatoms – 1-2 doses
Cyanobacteria – (Yes, it will outcompete another bacteria) 1-5 doses
Dinoflagellates – 2-5 doses
Bubble algae – 3-8 doses
Hair Algae – 3-5 doses (depending on species of hair and how bad the infestation is)
Turf Algae – 8-20 doses ( again, depending on species and how bad the infestation is)
Bryopsis – 6-30 doses ( again, depending on species and how bad the infestation is)

Jeff Jacobson
Owner – Underwater Creations, Inc.

TBR Recommends

Vibrant Aquarium Cleaner comes in 8oz and 16oz bottles.

This great product is getting fantastic results and the many owners in the forums are confirming this!

To Finish

Like many of the algae’s we face in our aquariums, some of the treatments work great for one aquarist and not so well for someone else. This was the reason I wanted to give you all the proven ways to get rid of this very stubborn pest so you can try each one until you find a solution that works.

As technology advances, we are seeing more products that are getting better and easier at targeting our problem areas and helping to solve them! For Bryopisis, a single $20 purchase could now save you some serious sanity!

Algae is just a part of owning a saltwater aquarium, but early detection and eradication is going to make this hobby far more enjoyable for you!

Further Reading

If you found this helpful please be sure to check out some of our other articles all designed to help you!


Hi, I'm Richard and I have been an avid aquarist for over 30 years with a passion for Saltwater Aquariums. I love to pass on my knowledge to help others get the same amount a pleasure out of this hobby as I do. View my About Me page to find out more about me & my mixed reef aquarium.

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