Temperature is one of the biggest levers in guppy keeping. A few degrees can change appetite, growth rate, breeding frequency, and even how quickly waste builds up in the tank. Many keepers aim for a stable middle range, but in real homes temperatures can drift seasonally. Understanding what happens at cooler vs warmer temperatures helps you adjust feeding and maintenance rather than being surprised by changes in behaviour.
Running cooler (around 22–23°C)
- appetite slows and fish may appear less “busy”
- growth rate is slower
- breeding often slows down
- oxygen is generally easier to maintain, but fish still need stability
Running warmer (around 25–26°C)
- appetite increases and fish are more active
- breeding and fry growth often speed up
- waste load rises faster, so maintenance discipline matters more
- oxygen demand increases; surface agitation helps
The real danger: instability
Guppies tolerate a range better than they tolerate constant swings. Sudden temperature changes can trigger stress responses (clamped fins, appetite loss). Aim for stable control rather than chasing a perfect number.
If your tank runs cooler in winter, feed a bit less and accept slower growth. If your tank runs warmer in summer, increase aeration and watch feeding so water stays clean. Small adjustments keep guppies thriving year-round.
