Moving guppies between tanks seems simple: net fish, move them, done. But many “mystery losses” happen right after transfers. The cause is usually shock — temperature differences, pH/KH differences, or stress stacking from chasing fish around with a net. The safer approach is to treat a tank-to-tank move like a mini acclimation, especially if the tanks are maintained differently.
What causes shock during transfers
- Temperature mismatch: small tanks swing quickly, so differences are common.
- Mineral mismatch: KH/GH differences can stress livebearers fast.
- Chasing stress: fish burn energy and stress hormones spike during long net chases.
- Oxygen changes: warm or crowded holding containers lose oxygen quickly.
The safest “mini acclimation” method
- prepare a clean container with water from the source tank
- move fish into the container gently (minimal chasing)
- add small amounts of destination tank water over 15–30 minutes
- net fish into destination tank and discard transfer water
Transfer tips that reduce stress
- dim the lights
- avoid feeding right before a big move
- don’t combine a move with a major rescape or deep clean on the same day
- keep aeration available if holding fish for longer than a few minutes
Moving guppies should feel calm and predictable. If you treat transfers like acclimation and you avoid big swings, fish settle faster and you avoid the sudden post-move losses that frustrate so many keepers.
