Spider wood is the pale, root-like driftwood that branches out into fine tendrils. It is sold as the root of Rhododendron, or azalea, shrubs, and it suits the Nature Aquarium look because its branching reads as tree roots or bare winter growth at tank scale.
What spider wood is
The trade name covers the roots of Rhododendron, the genus that includes azaleas, which is why you also see it sold as azalea root or redmoor root. Terrarium Tribe and Tannin Aquatics both identify it that way. Tannin Aquatics adds that the exact species and origins are kept “shrouded in a sort of deliberate mystery”, so treat any more precise claim on a product listing with some caution.
It will float at first
Spider wood is lightweight, so it will almost certainly float when it first goes in. That is normal and temporary.
There are three ways round it. Soak it in a separate container until it takes on enough water to sink, which Terrarium Tribe warns can take weeks. Boil it, which helps it sink faster. Or weigh it down in the tank with a piece of dragon stone or another rock and let it waterlog in place.
How long to boil spider wood
It depends what the boil is for. To clean the wood, Terrarium Tribe recommends 15 to 30 minutes, if you have a pot big enough to hold the piece. To draw tannins out before the wood goes in, Buce Plant recommends boiling for at least one to two hours.
Tannins and tinted water
Like other driftwood, spider wood releases tannins that tint the water amber or brown. Sources disagree on how much. Buce Plant says it releases fewer tannins than other aquarium driftwood, while Tannin Aquatics describes it as releasing a lot. Plan for some tint either way.
Whether the tint is a problem is up to you. Aquasabi suggests filter media such as Seachem Purigen, or simply sitting it out while your regular water changes clear it. Soaking the wood outside the tank for a few days to weeks before use also reduces it. Some keepers want the tint, and a blackwater biotope is built around it.
The white fuzz is harmless
A white biofilm commonly develops in a new spider wood aquarium during the first few weeks, and it looks alarming. Buce Plant calls it harmless and says it disappears on its own. Shrimp and snails graze on it, so there is no need to pull the wood out and scrub it.
Planting on it
The fine branching is ideal for epiphytes, which attach to surfaces instead of rooting in substrate. Tie or glue Java fern, Anubias, or Java moss to the branches and let them take hold. Keep the rhizome above the surface rather than buried.
Spider wood questions
Does spider wood release tannins?
Yes, though sources disagree on how much. Buce Plant says fewer than other aquarium driftwood, and Tannin Aquatics says a lot. Boiling it for an hour or two, or soaking it for a few days to weeks before use, takes some out first.
How long should you boil spider wood?
Terrarium Tribe recommends 15 to 30 minutes to clean it. If you also want to draw out tannins before it goes in, Buce Plant recommends at least one to two hours.
Should I remove the white fuzz on my spider wood?
No need. Buce Plant describes the white biofilm as harmless and common in the first few weeks, and says it disappears on its own. Shrimp and snails will graze it in the meantime.
Sources: Buce Plant, Spiderwood; Terrarium Tribe, Spider wood guide; Tannin Aquatics, The tangle of Spider Wood; Aquasabi, Driftwood in a tank with invertebrates; Aquasabi, Types of hardscape.