Fasting a fish before transport: useful or pointless?
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
Many fishkeepers have heard that a fish should not be fed the day before transport. This recommendation comes directly from professional live fish transport practice, not just an unfounded habit.
Contents · 5 sections
A long-documented practice
The reference technical report by Rudolf Berka for the European Inland Fisheries Advisory Commission, published in 1986 as "The Transport of Live Fish: A Review" (EIFAC Technical Paper No. 48), recommends a 24 to 48 hour fast before any extended live fish transport. The goal is not to make the fish lose weight, but to limit waste production during the trip.
Why it changes water quality in the bag
A fish fed right before departure keeps digesting and excreting during transport, in unfiltered water at a fixed volume. Waste and ammonia from digestion then build up directly inside the bag, compounding a problem that is already present — see our guide on ammonia and its toxicity for why this parameter is the most closely watched one during transport.
How long to fast, and for whom
A 24-hour fast is enough for most short trips (under four hours); for a mail-order shipment or a multi-hour trip, 48 hours is preferable. This practice applies to healthy adult fish: it is not advised for young fry or fast-metabolism species, which are more vulnerable to prolonged fasting.
What fasting does not replace
Reducing waste in the bag does not remove the need for other transport precautions: stable temperature, a limited duration and possibly added salt are still needed alongside it, as covered in our guide on the physiological stress of transport.
- 24 hours of fasting for a short trip, 48 hours for a long one
- Not advised for fry or fast-metabolism species
- Fasting reduces waste, it does not replace other transport precautions
- Resume normal feeding once arrival and acclimation are complete
For the full range of transport precautions, see our travel and safety hub.
Frequently asked questions
Should a fish also be fasted before a simple tank move at home?
Not needed for a few minutes' move between two tanks in the same room; fasting matters mainly for multi-hour trips in a sealed bag.
Does a 48-hour fast risk a health problem?
No, for a healthy adult fish a two-day fast is safe and commonly practised in both aquaculture and the hobby.
Should shrimp and snails also be fasted before transport?
The principle is less documented for invertebrates; their slower metabolism already produces little waste, though a short 24-hour fast remains a reasonable precaution.
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This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.