The short answer
Tannins are the harmless amber compounds that leach from driftwood, leaves and peat, tinting your water like weak tea. If the look bothers you, remove them with activated carbon in the filter and regular water changes; pre-soaking or boiling new driftwood stops most of them at the source. But know that tannins are not harmful — many soft-water fish and shrimp actually prefer this “blackwater” look, so removing them is purely cosmetic.
Why the water goes brown
New driftwood is the usual cause, releasing tannins for weeks or months until it’s spent. Botanicals like catappa (Indian almond) leaves, alder cones and peat do the same on purpose. The tint is a sign of natural organics, not dirty water — your parameters can be perfect while the water looks like tea.
How to clear it
- Activated carbon — the most effective fix; a fresh batch in the filter pulls tannins out within days. Replace it when the colour returns.
- Water changes — dilute the stain steadily; larger or more frequent changes clear it faster.
- Pre-treat driftwood — soak or boil new wood before adding it, so most tannins release outside the tank.
Browse media and carbon options in the filters hub.
Consider keeping them
Before you fight the tint, consider embracing it. Blackwater conditions suit tetras, rasboras, bettas, apistogramma and many shrimp, bringing out richer colours and natural behaviour. If you’d rather soften water this way on purpose, see softening water and the substrate and hardscape hub. More in the water testing hub.