The best acclimation is gentle, short, and consistent. Shipped guppies usually arrive with elevated waste in the bag water. If you stretch acclimation for too long, you can accidentally expose fish to rising ammonia once the bag is opened and oxygen levels change.
Before you start
- Turn the tank lights down (or off) to reduce startle stress.
- Make sure the tank temperature is stable and the filter is running.
- Have a clean bucket or container ready.
Step 1: temperature match (15–20 minutes)
Float the unopened bag for 15–20 minutes. This prevents temperature shock, which is one of the fastest ways to trigger clamping and stress.
Step 2: quick health check
Without shaking the bag, look for upright swimming, normal breathing, and fins that aren’t shredded. Mild clamping is common and often relaxes once fish settle.
Step 3: measured dilution (no drip kit required)
- Open the bag and roll the edge so it sits open in a small bucket.
- Add about half a cup of tank water every 5 minutes for 20–30 minutes.
- Keep the process calm and avoid loud movement around the container.
This gradually adjusts pH and minerals without stretching the time fish spend in older bag water.
Step 4: net into the tank, discard bag water
Net the fish into the tank and discard the bag water. Don’t pour shipping water into your display tank — it can contain concentrated waste and can contribute to ammonia spikes.
First 72 hours: the “recovery window”
- Low light: keep lighting gentle on day one.
- Small feeds: offer a tiny meal once they’ve settled; don’t overfeed.
- Don’t deep-clean: skip rescapes and major maintenance for a week.
- Test if anything looks off: clamping, flashing, or gasping = test ammonia/nitrite first.
When to worry
If fish are unable to stay upright, are gasping heavily despite good surface movement, or you see rapid deterioration, isolate and stabilise oxygen immediately. But for most shipments, calm acclimation plus stable tank conditions leads to fish eating and colouring up quickly.
