Cool-season shipping can be very safe for guppies when temperature swings are controlled. The biggest risk in winter isn’t “cold water” by itself — it’s rapid temperature changes (cold porch → warm room → warm tank) combined with stress and low oxygen. A steady, calm routine prevents most problems.
What good winter packing is designed to do
- Slow temperature drift: insulation reduces rapid drops and spikes.
- Control oxygen: clean water and proper bagging helps fish breathe through transit.
- Reduce waste: fasting 24 hours before shipping keeps the bag water cleaner.
When the box arrives
- Bring it inside immediately — don’t leave it on a porch or in the sun.
- Open calmly and check whether bags feel cold or stable, but don’t rush straight into the tank.
- Float bags for 15–20 minutes to match temperature.
Acclimation that avoids winter mistakes
In winter, people often “over-acclimate” for hours because they worry about temperature. Do a standard temperature match, then a short measured dilution (add small amounts of tank water over 20–30 minutes). The goal is gentle adjustment without keeping fish in older bag water too long.
First-week temperature stability
Keep the tank at 24–25°C for the first week. Avoid placing the tank near windows or drafty doors. If the room is chilly at night, a foam board under the tank can reduce heat loss through the base, and a tight-fitting lid helps hold warmth.
Feeding and lighting
Feed lightly the first day (or skip if fish look stressed), then resume small regular feeds. Keep lighting gentle on day one so fish can settle.
When to be cautious
If bags arrive very cold, give fish extra time to temperature match, but keep the process calm and avoid large sudden swings. If you see heavy gasping after introduction, increase oxygen immediately (surface agitation, airstone, sponge filter).
Winter success is mostly about calm handling and steady temperature. Guppies settle quickly when you avoid big swings and keep oxygen high.
