Identification and Control of Nuisance Green Macroalgae in Saltwater Aquariums

The cultivation of green macroalgae in a saltwater aquarium or reef tank has many benefits. It is only when they are allowed to grow out of control that they then become a nuisance. Here are some of the more common forms of green algae classified in the Kingdom: Plant/Algae -->Phylum: Chlorophycota/Chlorophyta -->Class: Chlorophyceae that one may encounter problems with. Seeing that most of these algae are hairlike or similar in form, thrive on high intensity lighting and strong current conditions, refer to the standard control methods at the end of this article for treatment unless otherwise noted.

-->Order: Bryopsidales
-->Family: Bryopsidaceae
-->Genus: Bryopsis

• Many times referred to as Sea Ferns, these soft, feathery, light to dark green hairlike alga grow in clumps and are usually introduced into an aquarium on live rock. Bryopsis sp. produce chemical defenses which can be toxic to many marine animals. Therefore, herbivorous animals that naturally eat algae will often avoid this alga species. Using natural predators for control is usually preferred by most hobbyists, but finding the right types of Hermit Crabs, Blennies, Zebrasoma & Ctenochaetus sp. Tangs or other animals that might eat Bryopsis can be a real challenge. As one example, many Sea Slugs of the Elysia sp. feed specifically on Bryopsis, but may starve to death after it is all gone! The point is, if you do decide to use reef janitors, do your research carefully! The life of many of these animals depend on their specific dietary food requirements, or lack of them. Using standard control methods can be a simpler solution for many hobbyists. Species Photos: B. pennata, B. pennata.

-->Family: Derbesiaceae
-->Genus: Derbesia

• More commonly known as green hair algae, these grow as dense mats, sometimes with erect branched filaments on top, and may develop from a bubblelike stage similar in appearance to that of Valonia, which in turn leads to the common filamentous hair stage. Being closely related, Derbersia can be treated in the same manner as Bryopsis.

-->Order: Cladophorales
-->Family: Cladophoraceae
-->Genus: Chaetomorpha & Cladophora

• Chaetomorpha - Can grow as brushlike tufts with fine erect hairlike filaments, or as vast mosslike masses. They can overgrow everything, choking out the light and water circulation that corals, other algae and tank inhabitants need to survive. Use standard control methods. Species Photos: C. antennina, C. aerea.

• Cladophora - Usually darker green in color, these alga can grow fine hairlike or stiff brushlike branches, with thin or thickened filaments that form as tangled clumps. They can be attached, rolling or free floating clumps, or round patches on or under the sand. Can be removed by hand, as well as controlled by standard methods. Species Photos: C. vagabunda, C. prolifera, C. glomerata.

-->Order: Siphonocladales
-->Family: Siphonocladaceae
-->Genus: Cladophoropsis

• Dark green, hairlike coiled alga, very much same in appearance and character as Cladophora described above and can be treated in the same manner. Species Photos: C. membranacea

-->Family: Valoniaceae
-->Genus: Valonia, Ventricaria & Dictyosphaeria

• Referred to as Bubble algae, the Valonia, Ventricaria and similar Dictyosphaeria species are some of the most popular macro species cultivated by aquarists. However, they can grow fast in aquariums even under low or poor lighting conditions, and are NOT controlled by nutrient reduction. Because of these traits they can quickly become a nuisance if not properly maintained. Species Photos: Valonia aegagropila, Ventricaria ventricosa, Dictyosphaeria cavernosa -- Learn more about Bubble Macroalgae

-->Order: Ulvales
-->Family: Ulvaceae
-->Genus: Enteromorpha & Ulva

• Enteromorpha - related to Ulva, these green tubelike filamentous alga rarely cause problems in an aquarium because of their high light and nutrient needs, and are often quickly consumed by algae eating fish. They grow attaching to rocks and shells near shoreline areas. The best safeguard for control is to scrape any newly collected rocks or shells before introducing them into the aquarium. Species Photos: E. flexuosa, E.flexuosa, E.intestinalis.

• Ulva - Sea Lettuces are a good natural food source for herbivorous animals, but can thrive and grow quickly under intense lighting in nutrient rich waters. These alga can be harvested by hand, deminished by reducing the light source or turning off the aquarium lights for a few days all together, as well as reduce DOC's. Species Photos: U. expansa, U. fasciata, U. fasciata, U. lactuca, U. lactuca, U. lobata.

Time and time again we have discussed algae control, and unless otherwise noted, all of the above species can be treated by using standard control methods. For additional in depth information about this topic, refer to our Algae Control Resources to learn more!