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Plant Life In The Aquarium

Another huge post by Calilasseia ...

The dichotomy between the freshwater and marine aquarium is a pretty large one, even though certain key principles (e.g., the nitrogen cycle) are common to both. This dichotomy is acute in the area of plant life, and my aim here is to give an insight into the plant life of these two different aquatic systems.

Perversely from the standpoint of ease of maintenance, but correctly from the standpoint of taxonomy, I shall start with the marine aquarium. Why? Because the marine aquarium is the realm of the Algae. Algae are the most primitive of all the true plants, with a lineage stretching back almost as far as that of life on Earth itself, but their ancient and primitive status does not mean that they are lacking in diversity. Everything from unicellular creatures such as Diatoms, through to the Laminariales, which includes the Giant Kelp, belongs in the Algae: some specimens of Giant Kelp, incidentally, have been reputed to grow to 500 feet in length! Also present among the Algae are the Ulvales and the Caulerpales, two Orders that contain many of the macroalga species popular in marine aquaria, the Fucales (seaweeds known as "wracks", the Euglenales (which includes unicellular species responsible in some cases for algal blooms, in freshwater as well as marine environments subject to eutrophication), and the Class Dinophyceae, which includes the Dinoflagellates. This latter group of organisms includes Gymnodinium microadriaticum, one of the algae that live symbiotically with corals; another member of the Genus, Gymnodinium breve, responsible for 'red tides', containing an extremely powerful (and chemically complex - synthesised for the first time in 1992) toxin called Brevetoxin A, acting upon the central nervous system; and a host of organisms more usually thought of as pathogens causing disese. Amyloodinium ocellatum, the cause of Velvet in marine fishes, is a Dinoflagellate, as are the freshwater Oodinium species that are close relatives (and also pathogenic to fishes). This organism does possess chlorophyll, but only in minute quantites compared to the truly photosynthesising green algae, and has lost much of its photosynthetic machinery in pursuit of a parasitic lifestyle. But, it is an alga, it has chlorophyll, and also possesses fairly efficient locomotion capabiity courtesy of the two flagella (the Dinoflagellates gain their name because of this anatomical feature - all have two flagella). The good news for marine aquarists, however, is that a greater number of Dinoflagellates are welcome additions to the aquarium - in the form of zooxanthellae living in corals and certain anemones.

Consequently, the marine aquarist is somewhat restricted with respect to the choice of plant life suitable for the saltwater aqurium, because out of the relatively diverse Orders of macroalgae, some are simply impractical in the aquarium (e.g, the aforementioned Giant Kelp!), some have yet to be cultured successfully, and others are capable of transforming from decorative additions to nuisance organisms because they can actually grow too well in a marine aquarium. Some of these latter algae do, however, have uses - nitrate absorption in a refugium. Thus, the marine aquarist is generally introduced to Caulerpa, an algal Genus with numerous species, some of which are so diverse in form from the others that they don't even look as if they belong to the same Order, and Ulva, the Sea Lettuces. Beyond those two Genera, one may occasionally see certain Rhodophyta or red algae, but these are much more difficult in the main to cultivate, and research work continues upon many of these, some of which would be suitable for a marine aquarium if they weren't so damned hard to keep alive!

Related to Caulerpa are the Algae of the Genus Penicillus known commonly as Neptune's Shaving Brushes upon account of their appearance. Udotea and Avrainvillea comprise the sea fans, while Halimeda discoidea has acquired, upon account of its unusual appearance, the common name of "Baby Bows"! An unusual one worth looking out for, though probably best left to experienced marine aquarists, is Acetabularia, which upon account of the shape of its fronds, is known as "Mermaid's Wineglass", and is extremely attractive. However, as the science and art of the marine aquarium advance, more algal species are becoming available, and culture details being disseminated. We should soon arrive (if this has not already happened!) at the stage where textbooks are written devoted solely to marine aquarium plants, but I have yet to encounter any such tomes at this stage.

The freshwater aquarium, on the other hand, is predominantly the kindgom of the flowering plants. Out of the numerous species of aquarium plant, one, Riccia fluitans, is a Liverwort, another Vesicularia dubayana is a Bryophyte (moss), and probably no more than five species are Pteridophytes (ferns), of which by far the best known is Microsorium pteropus, the Java Fern. The remainder, some 80 species in one book I read recently, are all Angiosperms (flowering plants), belonging to a diverse range of Families. Among the best known are Vallisneria (Family Hydrocharitaceae), the Amazon Swords Echinodorus (Family Alismataceae), the Genus Cryptocoryne (Family Araceae), Cabomba (Family Cabombaceae), Myriophyllum (Family Haloragaceae) and Aponogeton (Family Aponogetonaceae). From the standpoint of evolution, this situation arose because the higher plants above the Algae evolved initially on land, whereupon some species gradually returned to aquatic environments that were almost exclusively freshwater. The only major Family of flowering plants to have adapted to an aquatic existence in the marine environment is the Family Zosteraceae, the Eel-Grasses, and these are specialised to put it mildly. One or two higher plants (most notably the ever-indestructible Java Fern) have adapted to brackish conditions, but in the main, the aquatic flowering plants are exclusively freshwater, and many are completely intolerant of salt full stop.

For the same reasons that freshwater fishes are easier to keep alive than marine fishes, freshwater plants are generally easier to cultivate than their marine counterparts. Like the freshwater fishes, they have had to evolve mechanisms for coping with seasonal changes, and local short-term disturbances such as rainfall diluting the mineral content of their homes, or washing organic detritus in from the surrounding land. The typical freshwater plant, therefore, has to cope with the same kind of environmental fluctuations as freshwater fishes, and while some have very definite obligate preferences with respect to pH and hardness just like the fishes, others have more widespread adaptability. Just as there are far more flowering plants cultivated on land than any other kind, flowering plants dominate the freshwater aquarium scene enormously, and these include some truly exotic wonders such as Aponogeton madagascariensis, the Madagascar Lace Leaf. Others are aquatic, but have evolved to produce emergent leaves (Waterlilies and the like, also the old favourite from the Innes book days, Sagittaria) and some are properly to be considered bog plants for a paludarium, which have a limited life if constrained to live as fully submerged aquatics. The true aquatics, however, are diverse, numerous, and in some cases adapt to the aquarium to the extent of producing their flowers: I have had Vallisneria flower in my community aquarium in the past, and it is possible, with care, to induce Aponogeton to flower, pollinate the flowers by hand using a fine artist's paintbrush, and cultivate the new plants from seed. More usually, however, propagation of aquarium plants is vegetative: Vallisneria will, in conditions to its liking, produce rampant runners all over the aquarium floor, resulting in a carpet of reedy leaves, and even the fussier Echinodorus species can be persuaded to reproduce similarly with due care and attention.

Consequently, the Algae, which dominate the marine aquarium as decorative plants and nitrogen cycle managers, are considered in the main to be nuisance organisms in the freshwater aquarium. As far as I am aware, there are no macroalgae comparable to the marine species to be found in the freshwater world, and the species that are found in fresh water tend to be either unicelllar (whether free-swimming like Euglena or as sessile colonies coating assorted surfaces such as some of the Diatoms), or in the case of multicellular algae, organisms such as the thread algae and blanket weeds that are an outright pestilence in ponds. Once classified with the Algae, but now known to belong to an entirely separate Kingdom of life, are those other organisms, the Cyanobacteria, formerly known as the Cyanophyta, whose lineage stretches back almost to the Hadean era, 3,500 million years ago, prokaryote cellular life forms that most strikingly manifest themselves in Western Australia as Stromatolites, but which form luridly coloured swathes of unpleasant-smelling slime in freshwater aquaria, and are equally undesirable in the marine aquarium.

Quite why no macroalgae have made the transition from sea to fresh water is something of a mystery, one of those evolutionary puzzles that will doubtless be answered in the fullness of time, but they have remained in the oceans, the sole source of green in the marine aquarium. In a way, their absence from freshwater is a pity, because the marine species are every bit as decorative as the higher plants such as Myriophyllum that the freshwater aquarist knows and loves: but the flowering plants have more than made up for this absence in their diversity of form, and constitute a body of aquatic greenery that, when planted sensitively in an aquarium, can help create that wonderful 'window on the underwater world' look that so many of us strive to achieve. Whichever aquarist one happens to be, freshwater or marine, the plants available to us enrich our aquaria enormously, providing not only beauty of form, but valuable services, as havens for fishes needing shelter, in some cases as nurseries for their young, and the most valuable service of all, as consumers of nitrates at the end of the nitrogen cycle. Other than in specialised setups, where they would be eaten by herbivorous fishes, destroyed by fishes such as large open-water spawning Cichlids, or in strongly brackish aquaria where they would perish, the freshwater plants have a place in every aquarium; while the marine aquarium can be vibrant and lush without them, soft corals swaying in the current, and hard corals extending flower-like polyps in spectacular displays, how much easier it is to control nitrates when they are present, even if only in a refugium.

Welcome to the world of aquarium plants. One every bit as exciting as that of the fishes they are cultivated to live amongst!



Panda Catfish fan and keeper/breeder since Christmas 2002

Always a good read Calilasseia, keep up the good articles!

Algea in the freshwater planted tank is quite a nuissance, as I know well, but I think if your plant tank is started right algea can be diminished and the window to the underwater world, as I think you put it, can be acheived.

In my ecology lab we dissected a holdfast(root-type structure) of the giant kelp and found biodiversity within a few square feet that rivals that of any ecosystem save the rainforests and reefs. So algeas are most definitely more than just nitrate reducers!

Last edited by mattyboombatty at 14-Jan-2005 11:13

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Critical Fertilator: The Micromanager of Macronutrients

Great stuff Calilasseia! Someone must have done a water change on your brain, you're posting articles as often as you mention your corys having "fun" .

*mutters about algae*

^_^
Current [link=Contest Rules]http://www.fishprofiles.com/files/forums/Aquascaping/44382.html?200412022138" style="COLOR: #EB4288[/link][/font]

That one made me laugh BabelFish ... water change on the brain

Actually, I'd like to be here in the forums more, but I rely on public networks for my net access, so my time is severely restricted.

One day I'll get broadband at home ... then you'll be sick of the sight of me

Matty, I'll add your comments to the knowledge base.

Panda Catfish fan and keeper/breeder since Christmas 2002