Slow losses without testing ammonia or nitrite
This looks like: chronic ammonia and/or nitrite exposure
Why this happens
Fish adapt until they can’t. Bodies shut down quietly — clamped fins, faded colours, then one fish every few days. You cannot smell safe water reliably.
What to do right now
- Buy or borrow a liquid test kit today — ammonia and nitrite strips are better than guessing.
- If either reads above 0: 30% water change with matched, dechlorinated water; repeat until readings fall, spacing 12–24h.
- Stop feeding heavy until nitrite is 0 and ammonia 0 for 48h.
- Vacuum visible waste if you can without nuking filter media — squeeze sponge in old tank water, not chlorinated tap.
- Track results on paper — App-aquatic free logging can catch trends earlier next time.
What not to do
- Don’t trust “clear water = healthy water.”
- Don’t add more fish until the cycle is stable.
Stop it happening again
Own a liquid test kit and test roughly weekly, especially in a tank's first months. Clear water is not the same as safe water.
If that doesn’t fix it
If tests stay perfect yet deaths continue, move to disease diagnosis with sharp photos.
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.