Guide
Adding wood to a tank: water changing color? Here’s what’s going on
Your water turns tea-coloured or brown after adding driftwood. It’s tannins — and they’re usually harmless. What causes it and what to do.
What’s happening
Wood releases tannins (humic acids) into the water. They’re natural compounds found in bark, leaves, and wood. When you add driftwood, bogwood, or other aquarium wood, tannins leach out and tint the water yellow, amber, or brown — like weak tea or iced tea. It’s normal and expected, especially with new wood.
Is it harmful?
No. Tannins are not toxic to fish, plants, or invertebrates. In fact, many species (tetras, rasboras, discus, bettas, some cichlids) come from blackwater or tannin-stained habitats and may feel more at home in slightly tinted water. Tannins can also slightly lower pH and soften water over time, which some fish prefer. The main “downside” is cosmetic: you may not like the look.
What to do if you want clearer water
- Soak the wood first: Before adding wood to the tank, soak it in a bucket or tub for a week or two, changing the water daily or every few days. That leaches out a lot of tannins before the wood goes in.
- Boil it: Boiling wood for 1–2 hours (or in batches if it’s large) speeds up tannin release. Do this in a pot you don’t use for food. Repeat if the water stays dark.
- Water changes: Regular water changes dilute tannins. Over time, most wood stops releasing as much — it can take weeks to months depending on the piece.
- Activated carbon: Adding activated carbon to your filter can help remove tannins and clear the water. Replace it when it stops working.
Or embrace it
Some hobbyists deliberately create “blackwater” tanks with driftwood, Indian almond leaves, or peat to mimic natural habitats. The tinted water can look natural and reduce stress for fish that evolved in those conditions. If your fish are healthy and you don’t mind the colour, you don’t have to do anything.
Quick takeaways
- Tannins from wood tint water brown/tea-coloured. It’s normal and harmless.
- To reduce: soak or boil wood before adding; use water changes and activated carbon.
- Many fish actually prefer slightly tinted water. You can leave it if you like the look.