Using wood and roots

Wood and roots. For movable plants grown on bogwood ...or on rocks, see "Using plants" in this folder.
 
"Bogwood" and "Driftwood." Roots, like rocks, anchor the sometimes flimsy compositions offered by plants alone. In a former version of his website, Takashi Amano noted how "pieces of driftwood convey a sense of nature's time-scale — the long cycle of life — death — rebirth — of which we only glimpse fragments."
 
The real definition of bogwood is wood that has stood for years in an acidic peat bog and has consequently leached out its tannins and has acquired a dark color. Bogwood hasn't rotted, because the low pH of a bog discourages fungal spores and most bacteria.
 
"Driftwood" from saltwater beaches has been leached in saltwater and bleached by the sun to its familiar gray. Driftwood darkens when it's wet. But in truth most kinds of wood that have naturally weathered for a season or so, away from contact with the earth, which would tend to rot them, can also be used in aquaria. Avoid partly-rotted wood, for the fungi at work in it depend on air, and they will die in water and be decomposed themselves, and the results can overwhelm the aquarium. It is always a good idea to soak any wood in several changes of water before you use it in a fish tank. I don't feel that boiling is strictly required.
 
Weighting it. Driftwood may be frustratingly buoyant. If you are incorporating driftwood into your initial set up, you may need a weighted anchor for it. Bolting it to a slate paver is often suggested, but seems clumsy. You can anchor driftwood better by drilling a small hole through it and two more near the center of one of those big Tupperware lids that have lost their original container. You tie the driftwood to its tupperware anchor with a loop of monofilament. With the lid weighted with sand and gravel, your driftwood is less likely to drift. Large pieces may need to be anchored at both ends.
 
A smaller piece may just need a temporary weight to hold it down for the first month or so. A ZipLok bag filled with gravel and water makes a flexible "sandbag" that will hold a buoyant root in place until it has settled.
 
Don't use any fresh "live" wood or root or bamboo. Whatever the source, wood that is suitable for aquarium use must have first lost its greenwood and sap. Elements in the sap, even in dried sap, may pollute the water or be toxic to fish. The sap in wood all runs in the cambium layer right under the bark. The bark itself is corky and fairly inert, except for some tannins and other polyphenols. If you don't want a blackwater stain, it's always a good idea to strip away any remaining bark.
 
The part of wood that can be used in the aquarium is the weathered "skeleton" of wood, composed of cellulose, hemicellulose and lignin. These stable molecules are assembled from long strings of polysaccharides, linked by chemical bonds that break down only very slowly in water, by a combination of fungal and bacterial enzymes.
 
Most wood you choose will be safe once it's weathered, but I'd avoid "turpentiney" conifers, such as pine, fir, juniper, cedar, etc. Those sharp-smelling resins may turn out to be low-grade toxins.
 
Bamboo. Bamboo is a grass, not a wood. Grasses are not usually known for toxic alkaloids and terpenes, and still I've read of fish being poisoned by fresh-cut lengths of bamboo. On the other hand, I've also seen a recent article in Practical Fishkeeping about decorating with sawn lengths of bamboo. Perhaps the difference is in drying and curing. I'll hold my skepticism in reserve til I've heard your own first-hand experience. Or til I've experimented myself.
 
Links. Aquarium Driftwood is a web source for waterlogged roots, sent wet from Semmes AL and sure to sink for you if you don't let them dry out.  They've been in business for more than a decade. I haven't used these folks myself, but one of the aquaria they illustrate belongs to planted-tank guru Karen Randall. I'm disposed to like any outfit that offers, in addition to their picturesque centerpieces, a driftwood category "Bits and Pieces."
 
Waterlogging. Most wood floats because of air trapped within its pores and pits. Wood eventually sinks because fungi and bacteria degrade the pit membranes, increasing the wood's permeability. Wood fibers become saturated, but beyond their saturation point, which amounts to about 30% of the dry weight, free water is also present among the wood fibers, according to the McGraw-Hill Encyclopedia of Science and Technology, vol. 19, p. 580. Only a limited quantity of dissolved oxygen diffuses into these watery pores, and as it gets used up by bacterial respiration, there must be anoxic water trapped deep inside the pores and minute chambers of submerged wood.
 
You probably see what I'm getting at: some anaerobic de-nitrification quite probably occurs at deeper zones inside waterlogged wood. So, to what extent does wood in the aquarium reduce nitrate levels? I don't think anyone has explored this interesting issue.
 
Leached humins. Newly-introduced wood generally releases some humic substances such as tannins, which give the water a golden cast. Long submerged wood won't continue forever to discolor the water, but your patience may be tried in the interim. Fresh carbon in the filtration will take up the color. Strenuous boiling etc. isn't really necessary, certainly not from a hygienic standpoint, and it may be that boiling denatures proteins in the wood, making it more susceptible to breaking down, so that it lasts only a few years in the aquarium instead of decades.
 
Mopane wood. Since the 1990s the "bogwood" most generally on the market is mopane (Colophospermum mopane). Call it "mo-PAHN-eh" rather than "mo' pain" The "Welaby wood" with a tag attached that's been showing up at your LFS in recent years is also mopane, exported from South Africa: designer bogwood!
 
What is mopane? Throughout southern Africa, mopane is the predominant large tree that forms dense stands of woodland in low-lying river valley bottoms of the Zambezi and its tributaries. Mopane is a tree of the dry sub-tropical savanna rather than a rain forest tree. It's an important part of the savanna ecosystem, for its leaves are unusually high in proteins and the wood is hard and tough, the first choice for slow-burning firewood (according to Niles Eldridge, Life in the Balance, pp 10ff).
 
We want it in our aquaria for similar reasons: its density makes mopane sink even before it's become waterlogged, and it decays especially slowly. You might suspect that some protective oils are responsible for mopane's rot-resistance, like the oils that famously protect teak and mahogany. In 1995, students at the University of Zimbabwe's Department of Pharmacy working on an honors project found that oil steam-distilled from Colophospermum mopane had some antifungal and antibacterial properties in the laboratory: at the University of Zimbabwe website an abstract is .3 among"Student Publications" . 
 
Similar oils may make mopane unpalatable to Lory cats, like Panaque, that usually ingest wood fiber but leave mopane alone, as Robert T. Ricketts noticed.
 
"Mongo root" may be a fanciful term for mopane at your LFS, though "Mongo" is ordinarily the Papuan name for the nut of Pandanus utilis, one of the tropical screw-pines. I don't think Pandanus wood is commonly exported for aquarium use.
 
Teak. I'm reading that teak roots are being exported from Malaysia for aquarium use. When I found some weatherworn pieces, intricate and beautiful enough to suit a Sung scholar's desk, a Burmese friend told me that they are not actually teak, but a waterside dipterocarp forest tree.
 
Mangrove roots. In the Philippines, mangrove roots are used in aquaria.
 
Fungi on wood. Sometimes patches of whitish fuzzy Saprolegnia appear on bogwood that's recently been placed in the aquarium. Though wood in oxygenated water at neutral pH values is almost always decaying, however slowly that may be happening, you don't want to encourage visible patches of fungus. Resist any temptation to attack the fungus by adding something toxic to the water. Don't haul out the wood and boil it in saltwater either. Be patient. As the aquarium matures, fungus on wood won't normally trouble you; in fact, bacteria are much more prominent than fungi as bio-degraders in submerged environments.
 
Stronger light will encourage a thin coating of sessile algae, which soon brings the protists that feed on algae and on the fungal spores; the algae and bacterial polysaccharides form the basis of an increasingly balanced biofilm that will appeal to grazers like Crossocheilus siamensis or Otocinclus and other Lory catfish. And the result of their grazing is that, though the spores are everywhere in water, patches of fungal hyphae don't get a chance to develop. Tannins in the water reduce the bacterial and fungal load too, so it's possible that peat filtration would have some slight positive effect in controlling fungus.
 
But if fungus is bothering you in a new tank or on a fresh piece of sunken wood and you want to help the bacteria and biofilm crowd it out, try this:  grip a small toothbrush against a siphon tube and hold the bristles over the end opening with your thumb. You'll find with a little practice that you can gently brush off the patch of fungus while you simultaneously siphon the loosened bits away. Be selective. Don't disturb adjacent areas, where a bacterial film is establishing itself and crowding out fungal spores.
 
Sometimes newcomers to aquaria wonder whether some kind of polyurethane varnish might be appropriate in combating unwanted growths on submerged wood. Sealing wood in this manner will not preserve it forever. Anaerobic decay may set in. Meanwhile a sealant renders it less than useless to Loricariid catfish and other biofilm grazers. If untreated wood slowly decomposing over the years bothers you, stick with cast-resin lookalikes, and matte-finish ceramic "logs."
 
Using wood. Weathered fenceposts with holes bored in them will never cut the mustard, even if they've been sandblasted and bolted to a piece of slate. Good pieces of Mopane at the LFS have been split and riven, not sawn; they are full of natural splintery surfaces that will develop rich pastures of biofilm. In water the wood takes on rich mahogany tones, which present handsome contrasts of light and shade. While you're setting the bogwood in place, check the effect under the actual lights you plan to be using. Sometimes a small shift in the wood's position casts a much more telling shadow. Don't forget the possibility of burying part of the wood to give the impression that roots and stumps are protruding from bankside or streambed, for not all the wood found in water has been carried down from upstream.
 
In a natural stream, sand and gravel silt up behind a long-wedged piece of waterlogged wood. Notice how this works the next time you're checking out a freshwater stream. Recreate this idea when you want to establish a higher level of substrate at the rear of the tank or in a corner; bogwood will help the substrate hold its place, for unsupported gravel slopes always flatten out over time.
 
With a smallish piece of bogwood, you may want to saw off a section to provide one flat surface where you can firmly attach a suction cup. Then you can fix the piece of wood to the rear glass. This will give an illusion of more depth that you really have. If you do this, you'll want to be sure the juncture between the glass and the wood isn't visible, or folks will see how you cheated. You might not need more than a twist of Java Moss to wrap the joint. I don't like to see bogwood leaning against a side pane, though; it just emphasizes the arbitrary edge. But Takashi Amano has no problem with this, so who am I to be so fussy?
 
Bogwood can stand upright, as long as it is stable and, just as important, looks stable. Intricate rooty structures, breaking up the aquarium space, foster smaller effective territories, which means you can house more fish. And many freshwater fishes, especially loaches, instinctively like to squeeze into tight spaces. So, don't be limited by the simple arched or branching shapes a single piece of wood can give you. Two or more pieces of root can be fitted together and bound with monofilament to form arched structures and cavelike recesses. The monofilament will be even less visible if you predrill the wood and thread the filament through a small section, rather than wrapping it round the wood.
 
Grapevine stumps. If you live in grape-growing country, McDaphnia suggests using the twisted and knotted stumps of pulled grapevines. What a resource, eh! Make sure that the stumps have been weathered in sun and rain for a year or so. An old wisteria root would do too. The toxins are in greenwood and sap and resins, remember, not in the universal cellulose and lignin.
 
Twiggy brush. Sometimes you want to have an area broken up by twiggy brush. Nancy Sweeney wrote to me about using twiggy oak branches, "Yes, oak branches. I try to get dried-up ones. I scrape the bark and moss off of them and just dump them in the tank. I've never had a dry one show any 'fungus,' but any sap left in larger pieces may do that. Some of the tiny twigs get knocked off in the scraping but any from pencil size to 50-cent size are ideal. No need to boil or anything. Just make sure they are dry to begin with. I stand some across the back of the tank and have some lying on the bottom."
 
You can also get twiggy Manzanita branches, sold for terrarium use. Manzanita is very buoyant, so you'll have to lash it to a stone with monofilament.