THALLOPHYTES

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.