Driftwood, as most of us call it, can be very useful in an aquarium. It adds a decorative touch that makes the aquascape seem more natural, and some fish species appreciate some wood in their setup. After a while, beneficial bacteria will also colonize the wood. Unfortunately, it's not as simple as just plopping that piece of wood in the tank, which would cause the wood to release tannins into the water.
Tannins will be leached to some extent from most wood that you find in stores. They color the water, making it look like an Amazonian backwater stream. They also lower the pH, but don't expect this to cause a significant change in water that has a high pH. My hunk of wood hasn't made a large enough dip in the pH that it even shows up on my test kit. For more in depth information on tannins, click here.
So how do you prevent that nice piece of wood from fouling your water? the simplest way to do that is to soak the wood in water. Change the water every few days or so. The soaking method takes anywhere from a few weeks to a few months, but the norm seems to be a month or two. Keep in mind that you won't be able to remove all the tannins from the wood, and small amounts will be continually leached. By soaking the wood, you only reduce the amount leached until the tiny amount is unnoticeable.
To prevent more tannins from being leached, some people like to varnish the wood, but don't do this if you have any suckermouth type catfish. Most loricarids, commonly referred to as plecos, will chew the wood and graze on it to supplement their algae diet. They will end up sucking on the varnish, which may kill them.
Another way to deal with the problem of tannins is to simply soak the wood for about a week or so, and run activated carbon in the filter. Carbon will absorb the tannins, but the wood should still be soaked for a bit first to get at least some of the tannins off. This may not be the best method for planted aquariums, as carbon removes elements beneficial to plants.
Some interesting facts about wood: most of us simply refer to any piece of wood meant for aquarium decoration as simply driftwood or bogwood, but what does it really mean and what are we really buying?
One popular type of wood is mopani wood, which has interesting gnarled shapes. This type of wood comes from the mopane tree of Africa. This wood is generally prepared by soaking for a long time, then sanding it so it has a smooth surface. However, it still releases quite a bit of tannins.
Bogwood is wood that has been preserved in a bog under anaerobic conditions. Again, this wood will release the tannins, the organic matter that has built upon the wood over time. This wood has also been soaked for a long time.
Driftwood is literally driftwood, wood drifting in the water. Most wood you find for sale is either mopani wood or bogwood, and not real driftwood. Don't just go and pick one out of a river like you could do with rocks though, since all the other types of wood have been prepared through various processes, usually soaking for a long time, which removes fungi and other stuff to make the wood completely dead.
Brushwood is a type of wood that can be easily collected but is difficult to integrate into the tank aquascaping. Brushwood is essentially twigs and small branches. These woods should be allowed to dry completely before the soaking process. Once completely dry, they should snap easily, and there shouldn't be any green inside it. The aquascaping challenge comes from the fact that this wood floats and probably won't sink no matter how much you soak it. It can be weighed down with rocks, or left to float on the surface to provides cover for surface dwellers like gouramis.
I hope that that offered a more interesting look at the wood you use in your aquariums. Now that you know the difference between bogwood, driftwood, and mopani wood and also how to prepare them for aquarium use, you can fully enjoy your piece of wood, and so can your fish.
I set up a planted tank recently as was lucky to come across mopani and what was described as bogwood, but I know isn't. Anyway, I soaked both in hot water for about a week and they now look fantastic. There's a slight colour difference from my other tank, which is also planted but with no wood, but the water is still crystal clear. My upside down cat loves the bogwood and it's clearly his territory! I would recommend the effort in a planted tank with wood and rocks, no plastic in my set ups.
50 years of (mostly) successful fishkeeping has taught me to compromise. My biggest frustration was wood. Every morning I would take my shower with a 20 liter pail of soaking driftwood...for a YEAR! But the stuff would not waterlog to the point where it would stay down. I engineered a bunch of anchors but to no avail. My pet shop guy turned me on to fake driftwood. There is some really ugly stuff out there, but I found a plastic piece to satisify my needs AND it is chemically inert. The only compromise in my planted tank, it has developed a nice patina of healthy algae for grazing snacks and a hide-away for my shy Cory's. And rocks are for Cichlids!
I'm still a newbie, but I've added two pieces of found hardwood (downed tree branch) to my aquarium with great success by using a different method: boiling. I cut the wood down to fit in my largest pot, filled the pot with enough water to thoroughly cover the wood when it sunk, brought it to a boil, and left it boiling for a few hours (adding water as needed). Boiling for that long disinfects the wood, quickly releases most of the tannins, and waterlogs the wood thoroughly enough to sink. It's also much easier to remove bark after the wood has been boiled. Hope this helps!
I bought some mopani wood online at a cheap price (buyer beware) and was optimistic about the length of additional soaking needed. It remained in a bowl in the bath for 6 weeks with twice daily water changes but still began to stink! Obviously bacteria had developed so I baked it for 40 min at 200°C in the oven and 'hey presto' into the tank it went out of pure frustration at the length of time. It still leached colour for a month, but no further bacteria was evident or pH changes and it looks fantastic despite the hassle!
I've achieved good results with boiling both Mopani and Malaysian wood before adding to the tank. I used a small washtub on the stove, boiling it for at least 2-3 hours at a time in dechlorinated water then letting it cool before rinsing the wood and replacing the water to start again. With the Malaysian wood I noticed a reduction in the darkness of the water after a few times. With the Mopani I never noticed a reduction but did it 4 times before adding to to the tank. With the Mopani I also noticed some oily discharge as well as some slight whitish discharge while boiling. I've seen no discoloration and no bacterial growth on either piece.
Concerning tannins, while it is best to boil or soak the wood until leaching is minimized, the tannin is not harmful. In fact, it may be beneficial because of its slight antibiotic and anti-fungal properties. Along with the tannins, nutrients and trace minerals from the wood are also leached into the water, which benefits the fish. Using activated carbon in the aquarium's filtration system will help remove the tannins. To counteract the wood's tendency to lower the water's pH (making it more acid), the addition of calcium carbonate (sea shells or coral sand) to the tank will counteract the effect and balance out the pH (but also raise water hardness). Avoid pine and driftwood from the ocean. The pine has a stronger effect on the pH and tends to make the water smell like turpentine. Ocean driftwood is permeated with salt, which some fresh water fish cannot tolerate. Finally, regarding Mopani wood, I refuse to use it and urge others to do likewise. The cutting of Mopani wood, an African wood, is reported to be causing problems with the African natural environment due to deforestation. The less demand there is for the wood, the less the deforestation that will occur. If there is no demand for Mopani wood, then cutting it will all but cease. Why be an accomplice in the ruining of an entire continent's environment for the sake of a piece of wood for your fish tank when there are many other woods from which to choose that will be just as satisfactory?
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