Skip to content

Handling gear: nets, bowls, socks and microscopes

By the koi.wiki editorial team · Updated

Key facts: Handling gear covers the nets, bowls, holding socks, transport bags and microscopes used to capture, examine, and move koi with minimal injury and stress.[1][2]
Handling koi involves specialized gear designed to reduce physical damage and stress, since capture and confinement are considered unavoidable stressors in fish culture[1]. Equipment ranges from soft knitted-mesh nets and viewing bowls to transport bags, holding socks, and microscopes used for close examination of skin, gills and parasites[1][2].Best practice guidance from aquaculture extension sources emphasizes speed, gentleness, and minimizing the number of times fish are removed from water[1].

Nets

The Southern Regional Aquaculture Center recommends using knitted mesh dip-nets rather than knotted nets, since knitted mesh reduces injury and scale loss during capture[1]. Net mesh size and material should be matched to the fish being handled; treated nylon or polyethylene nets are recommended for seining, while soft knotless nylon mesh is advised for more delicate fish[3]. According to University of Florida IFAS Extension, seine nets used for harvesting ornamental fish are typically 20 to 50 feet (about 6 to 15 meters) long and 6 to 8 feet (about 1.8 to 2.4 meters) deep, made of nylon or polyester with a knotless weave to minimize injury, and are often fitted with extra floats and weights compared to standard food-fish seines because small ornamental fish can otherwise escape over or under the net[4]. Cast nets are noted to be effective and quick but can abrade skin and cause scale loss, making them a less gentle option than traps or seines[4]. Kodama Koi Farm, a US koi dealer, advises that keepers should be patient and coax koi into netting rather than chasing fish, since forcing or chasing koi into a net can increase stress[5]. Copper alloy netting materials are also used in aquaculture because they resist biofouling, which can reduce the frequency of costly net changes and provide a cleaner environment, according to a general aquaculture source[8].

Bowls and holding tanks

Viewing bowls and holding tubs are used to examine koi out of the pond and to stage fish before transport or sale. Kodama Koi Farm states that every piece of equipment used at its facility, including tubs and nets, is disinfected after each use, and that only trained staff are permitted to handle koi, nets, or water to reduce contamination risk[9]. Southern Regional Aquaculture Center guidance similarly recommends thoroughly cleaning and disinfecting nets and equipment, for example by immersion in a 1 percent formalin solution, particularly when moving between facilities to avoid introducing pathogens such as the bacterium that causes motile Aeromonas septicemia[10]. Holding vats are also used to grade, clean, and sort fish before shipment[3].

Harvest socks

A harvest sock is a mesh confinement device used to concentrate fish, often during pond seining or harvest, so they can be more easily removed or transferred. According to the Southern Regional Aquaculture Center, paddlewheel aerators, including PTO-driven "sidewinder" units, are commonly used to produce a current of oxygenated water to sustain fish concentrated in harvest socks, since crowded confinement can otherwise lead to low dissolved oxygen[11]. Sock use also creates predation risk: wading birds such as the Great Blue Heron and night herons are noted to target fish that are confined in socks or nets because the fish become easy to access, and management guidance suggests hazing these birds away from ponds when fish are concentrated this way[12].

Transport bags and shipping boxes

For moving koi, Kodama Koi Farm describes a packing sequence of placing koi in a plastic transport bag with water, salt and a water conditioner, injecting pure oxygen, and sealing the bag with rubber bands before placing it in a box, aiming for the bag to sustain the fish for about 24 hours[5]. The dealer recommends keeping the koi's body covered by at least 90 percent water, adding about half a handful of salt and a water conditioner per bag, and triple-checking that bag closures are secure, since koi can work loose a partially open seal[5]. For tank transport, Kodama Koi Farm recommends filling the tank fully to avoid air space that could let koi jump and injure themselves, maintaining salt at about 0.3 percent (3 pounds per 100 gallons), and using pure oxygen or a battery-powered air pump[5]. The Southern Regional Aquaculture Center notes that commercial shipping boxes are typically insulated with polystyrene foam about 0.75 to 1 inch (1.8 to 2.5 cm) thick to maintain stable temperature, with a watertight plastic bag inside, and that fish should be held off food for at least 24 hours before shipment to reduce waste and regurgitation in transit[6]. Boxes should be labeled with species, contact information, and numbered sequentially within a shipment[6]. University of Florida IFAS Extension guidance for live fish sent to diagnostic laboratories similarly recommends packing fish in a heavy-ply plastic bag with about one-third water and two-thirds oxygen, placed in an insulated cooler with an ice or heat pack depending on ambient temperature[7].

Microscopes and diagnostic examination

A microscope is described by Kodama Koi Farm as an inexpensive and accurate tool for diagnosing koi health problems, allowing keepers to examine scales and skin in much greater detail than is possible with the naked eye[2]. Under magnification, keepers can distinguish rod-shaped parasites such as anchor worm from disk-shaped parasites such as fish lice (argulus), according to the dealer[2]. At a professional diagnostic level, University of Florida IFAS Extension describes a full fish necropsy that includes biopsies of skin, gill and fin tissue examined under the microscope primarily for parasites, along with squash preparations of internal organs examined microscopically for parasite infection, while bacterial, viral and fungal agents may be suspected microscopically but require confirmation by other laboratory methods[7]. Microscopic examination is also used to detect lymphocystis, a disease that does not affect cyprinids such as koi, by revealing enlarged cells in biopsied skin, fin and gill tissue of susceptible species[13].

Reducing handling stress

The Southern Regional Aquaculture Center lists several best management practices for reducing stress during handling and transport: using knitted rather than knotted mesh dip-nets, minimizing the number of times fish are removed from water, working as quickly as possible, and reducing water volume in tank systems where feasible to limit prolonged chasing during capture[1]. Stress hormones released during handling and transport can suppress fish immune responses, increasing susceptibility to disease, which is why minimizing stress during netting and confinement is considered important for disease prevention[1]. Kodama Koi Farm similarly recommends withholding feeding for about a week before a planned move to clear the digestive system and limit ammonia buildup in a bag or transport tank, and recommends a post-transport quarantine period, suggesting 2 weeks after a routine move and 3 to 4 weeks after returning from a show to monitor for disease[5]. For diagnostic submissions, UF/IFAS Extension recommends submitting three to five moribund (near-death) fish rather than fish that are already dead, since dead fish are rarely useful for diagnostic testing[7].

Common questions

What type of net is best for handling koi?
Knitted mesh dip-nets are recommended over knotted nets because the softer weave reduces injury and scale loss when fish are captured[1]. Mesh size and net material should also suit the size of the koi and the setting, following general warmwater fish handling guidelines[3].
Why are koi placed in a sock during pond work?
A harvest sock concentrates fish in a confined mesh enclosure, often with aerated water current supplied by equipment such as paddlewheel aerators, to keep oxygen levels adequate while fish are held before sorting or transfer[11]. Confinement in a sock does increase vulnerability to predation by wading birds, so ponds and socks are sometimes monitored or herons hazed away during this period[12].
How are koi typically packed in a bag for transport?
A US koi dealer describes adding water, salt, and a water conditioner to a transport bag, placing the koi gently, injecting pure oxygen, sealing with rubber bands, and placing the bag in a box, which it states can sustain a koi for roughly 24 hours if done correctly[5].
Do I need a microscope to diagnose a sick koi?
A microscope is described as a simple, inexpensive, and accurate tool that helps distinguish external parasites and assess scale and skin condition more clearly than the naked eye alone, according to a koi dealer's health guidance[2]. For a confirmed diagnosis, University of Florida IFAS Extension recommends working with a fish health professional or diagnostic laboratory, which performs detailed microscopic biopsies and cultures[7].
How long should koi be quarantined after handling or transport?
A US koi dealer suggests a quarantine period of about 2 weeks after a routine move, extended to 3 to 4 weeks after returning from a koi show, to monitor for signs of disease such as koi herpesvirus before returning fish to the main pond[5].

References

  1. ^ SRAC Publication No. 474: The Role of Stress in Fish Disease. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/474%20The%20Role%20of%20Stress%…. Retrieved November 2026.
  2. ^ HELP, Is My Koi Sick?!? Diagnose Symptoms & Fish Diseases - FREE Health Checklist. Kodama Koi Farm (koi dealer). kodamakoifarm.com/koi-sick-health-diagnosis-symptoms-diseases/. Retrieved November 2026.
  3. ^ 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.
  4. ^ UF/IFAS EDIS FA117: Harvesting Ornamental Fish From Ponds. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA117. Retrieved November 2026.
  5. ^ 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.
  6. ^ 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.
  7. ^ UF/IFAS EDIS FA055: Submission of Fish for Diagnostic Evaluation. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA055. Retrieved November 2026.
  8. ^ Aquaculture (Wikipedia). Wikipedia. en.wikipedia.org/wiki/Aquaculture. Retrieved November 2026.
  9. ^ 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.
  10. ^ SRAC Publication No. 478: Motile Aeromonas Septicemia (MAS) in Fish. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/478%20Motile%20Aeromonas%20Sept…. Retrieved November 2026.
  11. ^ SRAC Publication No. 3700: Pond Aeration. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/3700%20Pond%20Aeration.pdf. Retrieved November 2026.
  12. ^ SRAC Publication No. 400: Avian Predators at Aquaculture Facilities in the Southern United States. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/400%20Avian%20Predators%20at%20…. Retrieved November 2026.
  13. ^ UF/IFAS EDIS FA181: Lymphocystis Disease in Fish. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA181. Retrieved November 2026.