The short answer
Brown or tea-coloured water is almost always tannins — natural organic compounds leaching out of driftwood, botanicals or dried leaves in your tank. It’s completely harmless, and many fish actually prefer it. If you like the natural “blackwater” look, you can leave it; if you’d rather have clear water, it’s easy to remove.
What’s staining the water
The colour comes from tannic and humic acids released by organic hardscape:
- Driftwood — by far the most common cause, especially fresh, un-soaked wood.
- Botanicals — catappa (Indian almond) leaves, alder cones, oak leaves, added on purpose for blackwater tanks.
- Peat or certain soil substrates used in planted setups.
This is different from cloudy or discoloured water caused by waste. Tannin water is clear but tinted, like weak tea. If your water is murky rather than tinted, see why aquarium water goes cloudy.
How to clear it (if you want to)
- Run activated carbon in your filter — it adsorbs tannins and clears the colour within days. Browse our filter media guide.
- Do regular water changes to dilute and export the tannins over time.
- Pre-treat new driftwood by boiling or soaking it in a bucket for a week or two before it goes in the tank.
The natural approach
There’s no need to fight it. A tinted, botanical tank is a legitimate and attractive style, and the tannins benefit fish health. If you leave the wood in, the tinting fades on its own over the months as the tannins exhaust. Keep up your normal maintenance routine and let it settle. For a yellow rather than brown tint, see why aquarium water turns yellow.