Ubiquitous as no other

A pretty and delicate-looking seaweed, similar to a bird's feather. But with an incredibly fast growing rate and expandability, bryopsis is one of the major threats to the marine aquarium.

With outstanding reproductive capacity, bryopsis is able to multiply rapidly in a sexual way (by the union of male and female gametes) and asexual (releasing spores or by simply splitting a part of itself). It is such a resistant algae and its asexual reproduction so successful that it's not uncommon the occurrence of viable fragments in some herbivore's poop. This makes it a very ubiquitous algae, and in a few days it can spread to all nooks of the aquarium, even in the less illuminated and remote areas from the initial focus.

The other reason that makes bryopsis a extremely difficult to remove algae is the amazing ability to survive with ultra low nutrient levels. Bryopsis barely need any nitrates and phosphates to survive, it will just slow its growth to the fullest and stay in the aquarium while the rest of its inhabitants starve.

But if this were not enough, It happens to be monoical, which means that each algae presents both sexes. In this way, if conditions are favorable, they could (and in fact they do) surrender in a memorable orgy and spread themselves throughout the whole aquarium with little you could do.

Many aquariums have finished dismantled because of an uncontrolled growth of bryopsis.

Unappetizing and indigestible

To worsen things up, bryopsis does not seem to have an efficient predator. The few who try it seem to lose interest after the first bite, possibly due to the mild toxins that they contain.

Some slugs as elysia crispata seem to show some interest when there is no other food available, but their short lifespan and small size prevents them to be a great help.

Following with invertebrates, Some hobbyist have reported some success with sea urchins from tripneustes family. The most common, tripneustes gratilla, can eat small bushes of bryopsis if it is very hungry but won't be able to exercise real control over this plague and will end up dying before cleaning the aquarium. Other people state that emerald crabs, mithraculus sculpted will devour it, but there is no evidence that they can exercise a real control.

Regarding fish, some rabbit fish such as siganus vulpinus and siganus magnificent seem to exert some pressure when no other food is available, they might fail to eradicate it completely, but no doubt they will prevent or slow down its expansion.

Although it is unusual, bryopsis is also present as a pest in some coral reefs. This seems to be due to the human pressure performed on the few animals able to control their expansion, erosion and increased nutrients in areas near our settlements.

This algae can grow in the vicinity of corals, which will eventually die due to continuous rubbing against their tissues.

How to get rid of bryopsis in the aquarium

This is definitely the big question: getting rid of an organism that has barely any predators, is able to make it almost without any nutrient and has one of the best reproductive strategies in the plant kingdom.

It's posible.

Some years ago, by chance, a hobbyist found that rising magnesium levels above 1.600 mg/l bryopsis began to clear and finally die when approaching 2.000 mg/l. The product he used was Kent Tech-M. Interestingly other hobbyists raised their magnesium levels in their tanks, with different products, even above 2.000 mg/l without getting any positive results. Finally, it turned out that the product of the Kent brand incorporates a fortuitous pollutant (it is believed to be lithium) acting as algaecide and thus eliminating this undesirable pest.

There are some very powerful algaecides that weaken or even end up killing large amounts of bryopsis, Such is the case of AlgaeFix from API, Excital from EasyLife or Algae-X from Fauna Marin. The problem when using these algaecides is that they often kill all algae in the aquarium, besides of small microorganisms and bacteria. Many hobbyists have gotten rid of bryopsis just to start a probably worse battle: dinoflagellates. Furthermore, these algae killers do not use to be completely effective as after a few weeks, bryopsis comes back as if by magic.

But there is another method.

It is much slower, laborious and not always possible to implement, it will depend on the amount of rock and coral we have, and the level of affection by bryopsis.

It consists in weakening bryopsis to the maximum and then remove it by physical methods. Here are the steps to follow to get rid of this undesirable algae::

Reduce level of nutrients to the maximum. Bryopsis loses vitality and begins to turn light brown. There is no specific figure but usually achieved with nitrate concentrations below 0,5 mg/l
Remove the affected rocks and brush them in a bucket outside the aquarium. After brushing the rocks we must rinse them several times with clean water (ie from a water change). It is important not to release any trace of bryopsis in the aquarium and thus the rocks must return to the tank squeaky clean.
Lights out for at least four days. This will limit the chances of any piece or bryopsis spore that can cling to a rock and prosper.
Connect an UV sterilizer. With a slow flow it will kill all the bryopsis spores that might be free floating.
Score some hervivores that help control small outbreaks of bryopsis. Feed slightly in the coming weeks to maintain a very low nutrient system and force herbivores to eat bryopsis.

Repeat the process after two weeks.

You will make it with just two or three treatments as this described. The advantage of this method is that it does not eliminate other beneficial microorganisms and thus the system suffer lesser alterations.

As with most diseases and pests that threaten our aquariums, always the best strategy is prevention.

In this case, choose rock and coral of good quality and known origin, which look clean and have passed a quarantine period before introducing them into your aquarium. There are other complementary hygiene measures that must be considered, as giving a good brushing and subsequent rinsing with a solution of hydrogen peroxide (H2O2) for instance.

Finally insist that if we observe the emergence of a small clump of a feather-shaped algae, eliminate it immediately (brushing it away from the the aquarium to not spread it). Bryopsis spreads so fast that rarely gives second chances.