If your guppies suddenly refuse food after a water change, filter clean, or tank “tidy,” it’s usually a stress response — not instant illness. Guppies are routine-driven. When water temperature, chemistry, or environment shifts quickly, fish can clamp fins and pause feeding. The good news is this is often fixable within 24–48 hours if you check the basics in the right order and avoid making repeated big changes.
Common causes
- temperature mismatch: new water added colder or warmer than the tank
- chlorine/chloramine exposure: forgetting conditioner or underdosing
- pH swing: especially in low-KH systems
- too much disruption: major rescape or aggressive gravel vac
Quick checks
- test ammonia and nitrite (must be 0)
- confirm heater and temp stability
- ensure water was conditioned properly
- observe breathing rate and posture
What to do next
Keep lights low, provide calm flow, and offer a very small amount of food later in the day. Don’t keep adding new foods repeatedly; that just pollutes the tank. If water is stable and fish are calm, appetite usually returns quickly.
When guppies stop eating after a change, the best response is a calm checklist. Most cases are stress-related and resolve once stability returns.
