The Use Of Wood In Aquariums
By Andrea Watts - Why use wood in your aquarium? Pieces of cured wood/bogwood provide shelter for shy fish and spawning sites, as well as a visual centerpiece for the aquarium. Many plants that possess rhizomes instead of true roots require such structures for adhesion to grow. In addition, many sucker-mouth catfish require wood to rasp upon in order to aid digestion. It is also a viable way to provide the environment and water chemistry required by many soft water (black water biotope) species.
Sourcing the wood
Most LFS have pieces of wood for sale that are suitable for use in your aquarium. Some stores may have examples that have been pre-soaked. However the majority of pieces will probably require some degree of preparation before using in you aquarium. Most commonly you will find mangrove roots, eucalyptus species and pre-packed pieces from Africa and Asia (often wrapped in cellophane). The former type will probably contain less tannin than the latter two, however ultimately they are all likely to leach to a certain extent. The pre-packed pieces may have been treated with chemicals as part of the quarantine fumigation process on arrival to Australia. I tend to treat these pieces with suspicion.
Be aware that it is both irresponsible and illegal to remove wood in any form from its natural habitat. Offenders who are caught taking wood in any form incur heavy penalties. Even pieces that lay rotting on the ground provide important habitat sites for a myriad of native animals, and ultimately return nutrients to the soil upon their decomposition. Removal of wood from waterways (lakes, rivers, public dams and oceans) also falls under this category.
However, if you have access to wood from private farmland, or possess a firewood collector's permit, then you may find some suitable pieces. Most eucalyptus species are suitable, however not all natives are safe. Some exude dangerous oils and toxins once submerged, so care needs to be taken. Remember to carefully check the wood for geckos, skinks, spiders, centipedes, scorpions and other small animals before taking it from the site. Carefully remove any bark to reveal hidden organisms.
Wood recovered from riverbanks and waterways may possibly contain significant levels of herbicides, pesticides, salt or phosphate. Due to the porosity of wood fiber, these contaminants are soaked up and then released into the home aquarium. Do not use wood gathered from these locations if you are unsure about the inclusion of these chemicals.
Coconut shells and cork bark are also ideal for soft water situations.
Preparation for Use
Whether you have purchased or collected the wood yourself, it is essential to wash off any residual soil or other foreign particles. High pressured hoses, scrubbing brushes and a screwdriver are useful tools. Remove any moss or lichens, as some will release toxins into your aquarium. Soil often harbors harmful microorganisms and spores, so you need to be scrupulous in your cleaning regime. Wood of marine origin may have barnacles or mussels attached: they should be removed if they pose a threat to the inhabitants of the tank. Coconut shells should be free of fiber and nut residue.
These wooden items can be varnished for use in alkaline conditions, but check that none of your fishes has a taste for nibbling wood (e.g. Ancistrus spp.), as many varnishes are toxic if consumed. Wooden items have a disconcerting tendency to float until thoroughly waterlogged, and may need to be wedged into place with stones.
There is also an increasing range of simulations of wood, including resin and fiberglass replicas. These range from the remarkably realistic to the truly awful; fishes don't appear to be aesthetically affected, so the choice is up to you.
Tannin Description and Removal
Tannin (generally short for tannic acid) is an organic, dark substance that occurs naturally in most plant material. It is generally harmless to most fish. Rainforest biotope simulations benefit from the use of bogwood, coconut shells and cork bark. All of these will tend to leach tannins into the water, acidifying it and turning it brown; even in acid-water aquariums this can be too much of a good thing. Hence new materials of this kind should be ?aged? by soaking or leaving them outside to weather.
The amount of tannin that a piece of wood
contains is dependent on:
1. The species of tree from which it came;
2. The size/density of the piece;
3. The period of time which it has been separated from the tree (period of weathering); and
4. The source from which it is acquired (aquatic environment vs. terrestrial).
The following techniques are used to reduce
the level of tannin that is leached:
1. Small pieces can be boiled for 2 hours (the addition of rock salt can hasten this process);
2. Larger pieces can be weighted down and submersed in an old tub for a period of time. The water needs to be changed regularly to dilute the escaped tannins in the water;
3. The use of activated carbon in the filter will greatly reduce the visible coloration;
4. Purigen, a Seachem product, is highly effective in the removal of minute organic particles in the aquarium; and 5. Simply leaving it in outside to weather naturally.
It must be said that some pieces of wood will continue to leach tannin into the aquarium for many years after their addition. In this case, regular water changes will help to prevent the colour from becoming unsightly.
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