Driftwood in aquariums

Which wood types are safe for aquariums, how to stop them floating, how long tannins last, and whether to soak or boil. Practical prep and placement.

Wood gives a tank visual structure that rocks alone can't. It creates overhangs, caves, and branching forms that fish use as territory markers, hiding spots, and spawning surfaces. Epiphyte plants like Java fern, Anubias, and Bucephalandra attach to it and grow without substrate. And depending on the type, it can release tannins that soften the water, lower pH, and give the tank a natural amber tint.

Not all wood belongs in an aquarium, though, and even safe wood needs preparation before it goes in.

Types of aquarium-safe wood

Mopani

Dense, heavy African hardwood with a distinctive two-tone appearance (dark brown and tan). It sinks quickly because of its density, sometimes within hours, which is a major advantage. The downside: Mopani releases a lot of tannins. Expect dark water for weeks to months, even after soaking. If you want clear water, be prepared for extended pre-soaking or run activated carbon in the filter. If you want blackwater, Mopani is perfect.

Malaysian driftwood

Very popular, widely available, dark brown to black. Dense enough to sink readily. Releases moderate tannins. The irregular, gnarled shapes look natural in almost any setup. This is the "safe default" choice for most aquariums.

Spiderwood

Branching, root-like structure with thin limbs radiating from a central trunk. Creates dramatic, tree-like arrangements. The downside: it's lightweight and takes a long time to become waterlogged. Expect 1-3 weeks of soaking before it stays down on its own. Some pieces never fully sink and need to be anchored. Tannin release is lower than Mopani or Malaysian driftwood.

Spiderwood often develops a white biofilm within the first 1-2 weeks after submersion. This is harmless bacterial/fungal growth that snails, shrimp, and some fish will eat. It goes away on its own within a few weeks. Don't scrub it off and don't medicate for it.

Manzanita

Thin, elegant branches from a Western US shrub. Very hard and durable. It has a lighter color than most aquarium wood, ranging from tan to reddish-brown. Minimal tannin release. Like spiderwood, it's lightweight and needs extended soaking or anchoring to stay submerged. Manzanita is favored in minimalist aquascapes where the wood itself is the visual focal point.

Cholla wood

Actually dried cactus skeleton, not wood. Hollow and porous with a distinctive lattice pattern. It's soft and will decompose within 6-12 months underwater. Best used in shrimp tanks where the porous surface grows biofilm that shrimp feed on, and the hollow interior provides shelter. Not a long-term hardscape piece.

Bog wood

Wood that has been saturated in peat bogs or swamps, sometimes for years. Very dark, waterlogged, and heavy. It sinks immediately and looks ancient. Rich in tannins. Genuine bog wood is less common commercially than it used to be.

What to avoid

Don't collect wood from unknown sources without research. Softwoods (pine, spruce, cedar, fir) contain resins and saps that can leach toxic compounds into the water. Wood from urban areas may carry pesticide or herbicide residue. Wood from near busy roads may have absorbed exhaust particulates.

If you're collecting from the wild, look for hardwood that has been dead and drying for a long time. Remove all bark (bark rots quickly and fouls water). Avoid wood with visible fungal growth, soft spots, or any resinous smell. When in doubt, buy from aquarium suppliers who stock tested, safe wood.

Preparation

Cleaning

Scrub the wood with a stiff brush under running water. Remove loose bark, dirt, and debris. Don't use soap, bleach, or any chemicals. A dedicated scrub brush and plain water are all you need.

Soaking

Submerge the wood in a bucket, tub, or spare tank filled with dechlorinated water. Change the water every few days. This does two things: it waterlogs the wood so it sinks, and it leaches out excess tannins so they don't all dump into your display tank at once.

Soaking time varies dramatically by wood type and size:

Mopani: often sinks within 24 hours, but tannin leaching continues for weeks. Soak 2-4 weeks if you want minimal tannin release in the tank.

Malaysian: typically sinks within a few days. 1-2 weeks of soaking handles most tannin release.

Spiderwood: may need 2-4 weeks to sink. Some large pieces never fully waterlog.

Manzanita: similar to spiderwood. 2-4 weeks.

Boiling

Boiling accelerates both waterlogging and tannin release. A 1-2 hour boil in a large pot also sterilizes the wood. It's most useful for smaller pieces that fit in a pot. For large pieces that don't fit, pouring boiling water over them in a tub helps.

A common claim is that boiling removes all tannins. It doesn't. Boiling removes surface tannins quickly (the water turns dark brown in minutes), but deeper reserves continue leaching for weeks afterward. Boiling gets you a head start, not a complete fix.

Anchoring pieces that won't sink

If soaking and boiling don't make the wood stay down, you have options. Attach the wood to a flat piece of slate or stone using aquarium-safe silicone or stainless steel screws. Bury the base in substrate with rocks holding it down. Use fishing line or cotton thread to tie it to heavy stones, then hide the connection with substrate or plants. Some aquascapers use cyanoacrylate (super glue gel) to bond wood directly to stone.

Tannin management

If tannins aren't wanted, activated carbon in the filter absorbs them effectively. Replace the carbon every 3-4 weeks, as it becomes saturated. Purigen (a synthetic adsorbent) also removes tannins and can be recharged with bleach for repeated use.

If you want some tannin staining but not too much, skip the carbon and control the color through water changes. More frequent changes dilute tannins; less frequent changes let them build. Over time (months), tannin release from any piece of wood decreases as the extractable compounds are used up.

Effects on water chemistry

Wood lowers pH and KH slightly through the humic acids it releases. In a tank with moderate to high KH (above 4-5), the effect is negligible. In soft, unbuffered water, it can nudge the pH down noticeably. This is a benefit for fish that prefer acidic conditions (tetras, rasboras, dwarf cichlids) and worth monitoring if you keep fish that prefer alkaline water (livebearers, African cichlids).

Attaching plants

Epiphyte plants (Java fern, Anubias, Bucephalandra, mosses) can be attached to driftwood using super glue gel (cyanoacrylate), cotton thread, or fishing line. Super glue gel is the fastest method: apply a small blob to the plant's rhizome or root base, press it firmly to the wood, and hold for 30 seconds. The glue cures on contact with water and is fish-safe once set. Thread and line work too but take longer as you're waiting for the plant to grow its own attachment roots, which can take 4-8 weeks.

Don't bury the rhizome of Anubias or Java fern in substrate when attaching to wood. The rhizome needs to sit on top of the surface, with only the roots touching or gripping the wood. Burying the rhizome leads to rot.

The tank volume calculator is useful for estimating how much water volume large pieces of driftwood displace, which affects your actual stocking capacity and filtration needs.