Brown or tea-colored aquarium water is almost always tannins leaching from driftwood or dried leaves — cosmetic, not harmful, and actually intentional in some setups. Activated carbon in your filter clears it up if you'd rather have clear water.
What causes brown or tea-colored aquarium water?
Driftwood, dried leaves like Indian almond leaf, and other natural decor all leach tannins into the water over time, tinting it anywhere from a light amber to a dark tea color. New driftwood releases tannins fastest, tapering off gradually over weeks to months as it leaches out.
Driftwood is the most common source, but not the only one:
- Botanicals: Indian almond leaves, alder cones, and other dried leaves are added specifically to release tannins.
- Aquasoil and peat: nutrient-rich plant substrates and peat-based filter media can tint the water amber for the first few weeks after setup.
- Built-up organics: in a tank that's overdue for water changes, dissolved waste slowly turns the water a pale yellow. This version is a maintenance signal rather than a decor one — test nitrate, and if it's high, a few partial water changes will clear both.
Brown and clear, or brown and cloudy?
This is the quickest way to tell what you're dealing with. Tannin-stained water is tinted but transparent, like weak tea — you can see clearly through it. Water that's brown and murky or opaque is usually something else: substrate dust or mud stirred up during a rescape, or debris kicked up from a dirty filter. That kind of haze settles or filters out within a day or two and doesn't need carbon. If the haze is white or gray instead, see the cloudy water guide.
Is tea-colored water safe for fish?
Yes. Tannins are cosmetic, not harmful, and some fish species — particularly soft-water species like tetras and bettas — actually benefit from the slightly acidic, tannin-stained water it creates, often called a "blackwater" setup. Many aquarists keep it intentionally rather than treating it as a problem.
Do tannins lower pH?
Slightly, and how much depends on your water. In soft water with little buffering, heavy tannins can noticeably lower pH over time. In hard, well-buffered tap water, the effect is usually small enough to ignore. If you keep pH-sensitive fish and have just added a lot of driftwood, test pH weekly for the first month.
How long does driftwood leach tannins?
Most new driftwood leaches heavily for the first few weeks, then tapers off over one to several months. Dense woods like mopani can keep releasing color for longer than lighter woods. The color returning after every water change is normal during this period and gets fainter each time.
How to clear tannin-stained water
- Add activated carbon to your filter to absorb the tannins and clear the water. Replace it every few weeks, since it stops absorbing once saturated.
- Pre-soak or boil new driftwood before adding it to reduce how much it leaches once submerged. Boiling speeds the process up considerably.
- Do more frequent partial water changes if you want faster results without carbon.
- Leave it as-is if you like the look — it's purely cosmetic either way.
Tannins vs. other discoloration
| What you're seeing | Likely cause |
|---|---|
| Brown or amber tint, water otherwise clear | Tannins from driftwood, leaves, or substrate |
| Pale yellow tint, tank overdue for maintenance | Built-up organics — test nitrate and change water |
| Brown and murky after a rescape | Stirred-up substrate dust; settles on its own |
| White or gray haze/cloudiness | Bacterial bloom — see the cloudy water guide |
| Green tint | Free-floating algae bloom — see the green water guide |
Not sure which discoloration you're dealing with? Run the 2-minute water diagnosis to confirm, or see the full tannins guide for step-by-step fixes.