Brown or yellow tint
This looks like: tannins from botanicals — or less often, organic waste staining old media
Why this happens
Driftwood and leaves leach harmless tannins that acidify gently and tint brown. If sludge old filter socks never cleaned, you can get yellow-brown from waste instead.
What to do right now
- Sniff gently — rich earthy = tannins; foul = detritus.
- If new wood: water changes patience, or small bagged carbon for a week if you hate the look.
- If foul: service mechanical media, deep gravel vac open areas.
- Test pH drift if soft-water species depend on stability.
- Photograph before/after so you know what normal is for your scape.
What not to do
- Don’t bleach wood inside the tank — ever.
Stop it happening again
Pre-soak or boil new driftwood before adding it, and clean mechanical media on a schedule so waste doesn't stain the water.
If that doesn’t fix it
Sudden brown after adding rocks? Test for limestone or soil leaching.
Catch this earlier next time — log your water parameters in App-aquatic. Free forever.
This isn't veterinary advice - it's a directional read to help you decide your next step, based on the most common causes. We can't see your fish, so pair it with a liquid test kit and clear photos, and see an aquatic vet or a trusted local fish shop for a valuable or seriously ill fish.