Driftwood is a specific material, which undergoes several processes which make it several times lighter than its regular counterpart. In its lifecycle, it first lands in a body of water, be it an ocean, lake, or river. While it spends a sizeable amount of time there, it gets colonized by bacteria and algae, which decompose its organic matrix, namely lignin, and cellulose. Along with that, the water and salt erode its surface layer, stripping off its bark. Lastly, and most important, once driftwood inevitably drifts ashore, it gets bleached by the Sun, removing most if not all of the water it contains.
All of these things significantly remove organic and inorganic matter, leaving the driftwood significantly lighter than in its original state.
This loss of mass will also increase its buoyancy, which will always make driftwood float when it’s reintroduced into a body of water. This can be quite annoying, especially if you’re planning on using driftwood in an aquarium. But, if prepared properly, the wood you’re planning to use can be made to sink, and used without problems in a fish tank.
How can I make driftwood heavier?
To make the driftwood heavy enough to sink, we have to use a process called waterlogging. This means saturating the wood with as much water as it can absorb, thus eliminating its buoyancy and letting it be sinkable again.
To do this, simply place your driftwood in a bucket or similarly large container, and cover it completely in water. The length of this process can vary from three to five days, up to two weeks, in some cases even a month. This depends on the size, thickness, and density of your driftwood.
This process has the added benefit of drawing tannins out of the wood, which are naturally occurring chemicals that stain your water “tea-colored” and lower its pH level. Keep in mind that you should change the water every two to four days to ensure all the tannins are drawn out so that it doesn’t stain the soaking water anymore.
Once the water runs clear and the wood sinks into the bottom of your container, the soaking and waterlogging process is done, and your driftwood is ready to be used in an aquarium. Keep in mind that this is a mandatory process, as the pH change from introducing wood into your fish tank can be harmful, potentially even lethal to some species of fish.
My driftwood won’t sink, what should I do?
Some pieces of driftwood can be more stubborn than others, and retain their buoyancy no matter how long you soak it. This is a result of Archimedes’ principle that explains buoyancy, which states that an object will float if the weight of the water it pushes out is greater than its mass. Thus, pieces of driftwood with large surface areas will keep on floating.
There are several ways to remedy this. Firstly, you can try boiling your driftwood – 200°F for two to three hours, and then immediately soaking it in cold water, and letting it stay. This helps drive the air out and lets the wood soak more water into itself. This process can be repeated several times.
If this doesn’t help, with some planning and craftsmanship you can ensure the wood will stay on the bottom of your aquarium. Plan out how you want your driftwood placed, then you can either weigh it down with a large stone or lava rock. Be careful with how you place and anchor it, as you don’t want the rock to fall over onto your fish! You can also use a nylon fishing line to tie the driftwood to some sort of weight, be it a rock or something similar. This is generally a safer approach, and the fish line will practically be invisible once you have your whole setup covered with water.
Keep in mind that you should always soak your driftwood beforehand, to eliminate tannins and other chemicals out of it, and to saturate it with water, as you don’t want your setup to start moving and falling apart in your aquarium.