Suspected household fumes or spray reaching the tank
This looks like: airborne chemical absorbed through the water surface
Why this happens
Many aerosols leave oily films that block gas exchange and carry solvents. Fish lack kidneys like ours — they absorb what touches the gills fast.
What to do right now
- Stop using products in the fish room immediately — move tank maintenance away from fragranced air.
- Remove surface film: gentle paper towel skim or increased ripple; large 30–40% water change with matched, dechlorinated water.
- Run carbon in the filter temporarily if you already own media rated for aquariums — replace after a few days.
- Keep lids slightly vented unless you jump kids or cats — stale air beats perfume.
- Watch survivors 48h; note what was used for the vet or retailer if losses continue.
What not to do
- Don’t blast essential oil diffusers beside open tanks.
- Don’t “detox” with random salts — fix source and water first.
Stop it happening again
Keep aerosols, paint, cleaning sprays, scented candles and diffusers out of the fish room, and cover the tank before spraying anything nearby.
If that doesn’t fix it
If fish still crash with pristine habits, test ammonia and inspect heaters for stray voltage.
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.