What went wrong?

A few taps. No lecture. We narrow it down so you know what to do next.

Every diagnosis on this site

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Slow losses without testing ammonia or nitrite Brown or yellow tint Cloudy white — established tank Cloudy white / grey — new tank Pinecone appearance / raised scales Erratic swimming or spinning Filter stopped or flow collapsed Hiding nonstop Fluffy white patches (cottony) Foamy or bubbly surface Gasping at the surface, filter still running Green cloudy water Nothing changed — but fish died anyway Suspected household fumes or spray reaching the tank Temperature matched — but the tank still crashed Only the new arrivals die Not eating — more than a week Not eating — less than a week Slow deaths when you feed often Overnight deaths after the power went out (or flow stopped) Red streaks, sores, or ulcers Scratching on rocks / flashing Slow losses when feeding isn’t crazy Deaths right after new fish or plants Sudden deaths after a water change Tap water went straight in — no conditioner Cold or mismatched water after a change Torn, ragged, or disappearing fins White spots like salt or sugar