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Related FAQs: Marine Macro-Algae, Algae Can Be Your Friend

Related Articles: Avoiding Algae Problems in Marine Systems, Coralline Algae, Green Algae, Caulerpas, Coralline Marine Algae, Red Algae in General, Brown Algae, Blue-Green "Algae"/(Cyanobacteria)Diatoms, Phytoplankton, To Pest Algae/Control , Algae Filters ArticlesMarine Algae ID 1, Marine Algae ID 2, Marine Algae Control FAQs II, Marine Algaecide Use, Nutrient Limitation, Marine Algae Eaters, Culturing Macro-Algae; Controlling: BGA/Cyano, Red/Encrusting Algae, Green Algae, Brown/Diatom Algae

/A Diversity of Aquatic Life

Algae Can Be Your Friend, Pt. 1


By Bob Fenner


To Part 2

New Print and eBook on Amazon

Marine Aquarium Algae Control

by Robert (Bob) Fenner

Of all the topics asked of us on our websites, hobby venues and retail stores "maintenance" has got to be the biggest category. Algae in pest proportions in particular, is likely the number one cause of aquarist attrition. Not the livestock losing their lives; aquarists leaving the hobby!

               Is such strong emotion as fear or enmity deserving of such simple life? Are algae problems inevitable? Are they to be avoided, fought at all costs? The answer to all is a resounding no! With some care in setting up an aquatic system, regular maintenance, and especially, a bit of understanding about what algae are and how they make their lives in our tanks, you can make your peace with these organisms.

Algae: What Are They? 

            The most rudimentary algae are actually more closely related to bacteria (phylum Monera) than anything else. These Blue-Green Algae, aka Cyanobacteria share genetic, ultrastructural and metabolic features with microbes, being classed with the other algae on the basis of gross appearance and being photosynthetic. 

            The "true" algae are a part of the Protists (phylum Protista), not the "higher" real plants (phylum Metaphyta). Unlike metaphytans, algae lack vascular structures (xylem, phloem), leaves, roots… and are hence called thallophytes (subphylum Thallophyta) meaning "all about the same plant body" in reference to their lack of more specialized cells. Example: a vascular plant, Avicena, one of the Mangrove Trees, with true leaves, roots and a Brown Kelp whose cells all "do" photosynthesis, distribution, storage of foods, gasses…

Algal Groups: Divisions 

            As with all fields of endeavor, discussion of the algae involves its own set of arcane terminology. Micro- versus Macro- for instance is entirely a matter of subjective (human) appreciation. Micro-algae are so small that the human eye can't make out a cell that exists alone. Some groups of algae like Diatoms and Dinoflagellates are entirely micro-algae, whereas some of the Greens are Micro- and others Macro-algae. The larger "Kelps" are Red and Brown algae species and are very "Macro". 

            Phycologists (a largely U.S. term for folks who study algae scientifically) or Algologists classify the larger categories (termed Divisions, approximately the same taxonomic ranking as Phylum in Zoology) of algae by their photosynthetic pigment types, storage foods, locomotory structures and the make-up of cell walls.  Example, encrusting Micro- green and hundred plus foot stands of the Brown Kelp Macrocystis pyrifera.

Apparent color of algae can be deceiving (example: three views of Blue-Green Algae growths in aquariums appearing very different). The actual color of an algae depends on prevalent storage foods and photosynthetic pigments… can/does vary with growing circumstances, age… Microscopic examination can easily determine an algae to at least the Division rank.

As previously stated, the Blue-Green Algae are more closely related to Bacteria than the other, "true" Algae. As monerans they lack definitive nuclei, plasmids like chloroplasts, double-layered cell walls. Most appear black to bluish in color (though there are red, tan and other colors), and almost invariably are slippery, slimy to the touch.             The good news for aquarists is that BGA are out-competed easily in well set-up and maintained systems. Their presence almost spells trouble in "balance" of a system… a lack of circulation, aeration, too much nutrient, something missing in the way of competing photosynthetic life…

These are unicellular life forms that have two flagella (one mid-body, the other whipping around from their top) that are utilized for locomotion. The group includes the causative organisms for fresh and marine Velvet or Rust disease of fishes, as well as the at-times toxic Red Tide conditions found in the seas of the world from time to time.

These are the brownish scums, smears on the surface of the gravel, rock of many, especially new aquariums. On close inspection, you can make out individual cells or colonies that look like little boxes. These holey shells are used as diatomaceous earth in swimming pools, spas, even some types of aquarium filters due to the insoluble nature of their make-up (silicate) and porosity.

Marine species that include the largest kelps, encrusting forms, scroll like and leafy varieties. Some can be kept in captivity with attention to iodide supplementation and awareness of the types thermal, current needs.  Examples as shown.


            The most successful group of thallophytes on the basis of distribution, depth, bio-mass. Some Reds live below 100 meters in depth due to their range of photosynthetic pigments. Aquarists are familiar with the encrusting Red Algae called Corallines; there are some like the genus Porolithon that are important for actually building and holding the world's tropical reefs together. Other Reds play roles in human health (Gelidium alginates make petri plate culture possible) and manufacturing (as emulsifiers, stabilizers). Some are useful as human and fish food


The most desirable group of algae to aquarists for their beauty, diversity, functionality… due to the habitats they occupy in the wild, hardiness in collection, shipping, adaptation to vacillating captive conditions.

Some types are "bad" on the basis of their rapid growth, displacement of other species, lack of attractive properties.

Given water, light, nutrients… the allowance of other life, algae of different kinds is a foregone conclusion. Spores make their way into systems via the air, gear, recruited substrates, other livestock additions. You're going to have them whether you'd like to or not… What is up to you is how much of what types and where… along with the mental adjustment on your part that "cleanliness" is not sterility. There are still folks who bleach ornaments, wipe/scrub all down, even stoop to chemical algicides to keep their tanks "clean"… a foolish, counterproductive notion.

1) Optimize and stabilize a captive aquatic system, utilizing/bio-accumulating wastes, nutrients, fixing them into useful formats.

Act as bio-indicators, living test kits constantly monitoring water quality. For instance, no matter what your colorimetric assays tell you, believe the algae if there is not enough calcium, alkalinity for their use.

New Print and eBook on Amazon

Marine Aquarium Algae Control

by Robert (Bob) Fenner

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