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Shipping, bagging and acclimation

By the koi.wiki editorial team · Updated

Key facts: Koi are typically shipped in sealed, oxygen-filled plastic bags inside insulated boxes, and should be slowly acclimated to new water temperature and chemistry before release.[1][2]
Shipping live koi involves sealing fish in a container with a limited volume of water and oxygen that must sustain them until they reach their destination, so every step of bagging, boxing and temperature control affects survival.[1] Guidance from agricultural extension publications on ornamental fish transport, together with practices described by koi dealers, outlines how bags, boxes and oxygen are used, and why gradual acclimation (“tempering”) is necessary once koi arrive.[3][4]

Bagging and oxygen

Fish are placed into transparent polyethylene bags at least 3 mil thick, with 4-mil bags preferred by many commercial shippers for extra durability.[1] Square-bottom bags are generally favored over simple “pillow slip” bags because they sit flat, do not trap fish in sharp corners, and provide more surface area between the water and the oxygen layer for better diffusion.[1][3] After fish are loaded, ambient air is squeezed out of the bag and replaced with pure oxygen, since dissolved oxygen is often the single most limiting factor during shipment.[1][3] Bags are commonly filled so that oxygen makes up roughly 60 percent of the sealed volume, with some shippers using no less than half, and others at least two-thirds, oxygen to water.[1][3] A US koi dealer, Kodama Koi Farm, describes packing order as adding water, salt and a conditioner to the bag, placing the koi inside, injecting pure oxygen, and sealing the bag with rubber bands before boxing.[4]

Boxes and insulation

Bagged koi are usually nested inside an insulated box, most often made of polystyrene (Styrofoam) about 0.75 to 1 inch (1.8–2.5 cm) thick, which protects against rapid temperature change but is itself easily punctured or chipped.[1] That insulated box is then placed inside a rugged outer corrugated cardboard box for physical protection and sealed with quality packing tape.[1] One ornamental-fish supplier in Florida uses standard single polystyrene boxes around 17 by 17 inches for local shipments, sealed inside similarly sized cardboard outer boxes with a “live fish” stamp for longer trips by truck or air.[3] Heat or cold packs can be added just before sealing to maintain temperature during extreme weather or long layovers; chemical packs may last anywhere from under 8 hours to around 100 hours depending on type, and users are cautioned not to over-pack them.[1]

Temperature control during transport

Fish have a defined range of water temperature in which they thrive, and deviating from it causes stress while deviating beyond tolerance limits can kill them; shippers are advised to ship at the lowest optimal temperature for the species to slow metabolism and reduce the rate at which other water-quality factors deteriorate inside a sealed bag.[1] Lowering temperature during transport also quiets fish and increases oxygen saturation of the water.[7] Kodama Koi Farm notes that in cold conditions koi are slow moving and need little extra aeration because cold water holds more dissolved oxygen, whereas warm water holds less oxygen and requires more aeration effort.[4] According to the farm, Nishikigoi can adapt to a water temperature range of about 8–35°C (46–96°F), though the temperature considered suitable for them is 20–28°C (68–82°F).[5]

Carbon dioxide, pH and ammonia in the bag

Once a bag is sealed, fish respiration raises carbon dioxide levels, which can have a narcotic effect, interfere with oxygen uptake at the gills, and lower the pH of the water, compounding stress.[1] As carbon dioxide and ammonia build up during shipment, pH typically drops and the ratio of more toxic un-ionized ammonia to less toxic ionized ammonia shifts, so water chemistry inside the bag changes continuously from the moment it is sealed until it is opened.[8] Because nothing can be adjusted once a bag is sealed, planning for biomass, oxygen volume, trip duration and temperature in advance is treated as essential by extension publications on fish shipping.[1]

Stopping feeding and holding fish before shipment

Ornamental fish are commonly held for one to three days before shipping to allow them to clear waste from their digestive tracts, which reduces the amount of organic waste released into the shipping water.[3] Kodama Koi Farm similarly advises stopping feeding for about one week before a planned move, and holding koi in a holding or quarantine tank with little or no algae beforehand, in order to keep shipping water quality higher during transit.[4]

Acclimating koi after arrival

On arrival, fish should be "tempered" — slowly acclimated to differences in water temperature and chemistry — rather than released directly into new water.[2] One guideline calls for at least 20 minutes of gradual adjustment for every 10°F (about 5.5°C) difference in water temperature, with longer acclimation, up to around two or more hours, recommended when the temperature difference exceeds 10°C.[2][8] A common method is to float the sealed bag in the receiving water until temperatures equalize, then gradually mix in receiving water before fully releasing the fish; opening the bag too early lets the oxygen escape and forces a quick release.[2] Kodama Koi Farm describes a similar process of floating the bag in the pond to balance temperature, then gradually mixing in pond water, and suggests withholding food for 24 hours afterward while watching for signs of stress such as clamped fins or sluggish movement.[5] Fish that are properly acclimated typically swim off actively, while stressed or poorly acclimated fish may sink to the bottom or swim weakly, with mortality sometimes appearing hours to days after stocking.[2]

Quarantine after shipping

Because shipping and acclimation stress can increase susceptibility to disease, newly arrived fish are commonly held in a separate quarantine tank and observed daily for a period before being introduced to a main pond.[9] Kodama Koi Farm recommends quarantining newly purchased koi for at least 21 days, in a tank of roughly 100 to 300 gallons with a net cover, pump and filter, air pump, thermometer, and test kits for ammonia, nitrate and pH, with partial water changes of about 25 percent every two to three days if no filtration system is running.[5] Further detail on setting up and running a quarantine period is covered on the quarantine page.

Paperwork, costs and condition checks

Shipments crossing state or international borders often require health certificates or other permits, and requirements vary by state and destination country; obtaining disease-free certification for a facility can take years of prior negative testing.[1] Shippers are advised to confirm with the receiver, well in advance, which documents and certificates are required at the port of entry, since shipments lacking proper paperwork can be rejected on arrival.[1] Only healthy fish in good condition should be shipped, and tolerance for transport stress varies by species and size.[10] According to the US importer Kodama Koi Farm, shipping costs for koi typically range from about $99 to $330 or more per box depending on destination, weight and quantity, with additional cost for optional shipping insurance.[6]

Common questions

How much oxygen should go into a koi shipping bag?
Guidance for ornamental fish generally calls for bags to contain no less than half, and often at least two-thirds, of their sealed volume as pure oxygen rather than ambient air, since dissolved oxygen is usually the most limiting factor during shipment.[1][3]
How long should a new koi be acclimated before release?
A common rule is at least 20 minutes of gradual adjustment for every 10°F difference in water temperature, floating the sealed bag in the receiving water and then gradually mixing in that water before release.[2] Kodama Koi Farm notes that 10–15 minutes may suffice for acclimation alone, but recommends separate quarantine afterward since the koi's prior disease exposure is unknown.[4]
Should koi be fed before shipping?
Feeding is commonly stopped before shipment — extension guidance describes holding ornamental fish for one to three days to clear their digestive tracts, while Kodama Koi Farm advises stopping feeding about a week in advance to help keep shipping water quality high.[3][4]
What type of box is used to ship koi?
Koi are typically bagged in oxygenated water, placed in an insulated polystyrene box, and that box is placed inside a sturdy outer cardboard box sealed with packing tape for protection during handling and transit.[1][3]
Why do koi need to be quarantined after arriving?
Shipping and acclimation are stressors that can weaken immunity and allow disease to surface, so newly arrived fish are commonly observed in a separate quarantine tank, with one dealer recommending at least 21 days of observation and water testing before adding koi to an established pond.[9][5]

References

  1. ^ SRAC Publication No. 3903: Shipping Fish in Boxes. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/3903%20Shipping%20Fish%20in%20B…. Retrieved November 2026.
  2. ^ UF/IFAS EDIS FA013: Fish Fingerlings: Purchasing, Transporting, and Stocking. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA013. Retrieved November 2026.
  3. ^ UF/IFAS EDIS FA120: Preparation of Ornamental Fish for Shipping. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA120. Retrieved November 2026.
  4. ^ How Can I Safely Transport My Koi Fish?. Kodama Koi Farm (koi dealer). kodamakoifarm.com/how-can-i-safely-transport-koi-fish/. Retrieved November 2026.
  5. ^ How To Care For Your Koi Fish After Receiving It - Kodama Koi. Kodama Koi Farm (koi dealer). kodamakoifarm.com/koi-care-after-receiving/. Retrieved November 2026.
  6. ^ How Much Do Koi Fish Cost? Koi Pricing Guide for USA. Kodama Koi Farm (koi dealer). kodamakoifarm.com/how-much-do-koi-fish-cost/. Retrieved November 2026.
  7. ^ SRAC Publication No. 392: Transportation of Warmwater Fish: Procedures and Loading Rates. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/392%20Transportation%20of%20War…. Retrieved November 2026.
  8. ^ UF/IFAS EDIS FA119: On-Farm Transport of Ornamental Fish. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA119. Retrieved November 2026.
  9. ^ UF/IFAS EDIS FA181: Lymphocystis Disease in Fish. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA181. Retrieved November 2026.
  10. ^ SRAC Publication No. 390: Transportation of Warmwater Fish: Equipment and Guidelines. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/390%20Transportation%20of%20War…. Retrieved November 2026.