Observing New Koi on Arrival: What to Look For

By KoiQuanta Editorial Team|Updated Mar 2026

Experienced observers identify disease in new fish at arrival in over 60% of cases where disease is present. The difference between catching a health issue immediately and missing it lies in knowing exactly what to look for and being systematic about checking every area.

KoiQuanta's arrival assessment form covers all critical health observation points. No competitor has a structured arrival observation framework.

TL;DR

Total out-of-water time should not exceed 20-30 seconds.
The koi quarantine first 48 hours guide continues the protocol from where this arrival assessment ends.
KoiQuanta connects observations, water data, and treatment records in one searchable history.
Early detection based on parameter trends reduces treatment costs and fish stress.
Seasonal changes require adjusted monitoring schedules; automated reminders help maintain consistency.

Why the Arrival Assessment Matters

The first observation of new koi sets the baseline for everything that follows. If you don't observe carefully on arrival day, you can't distinguish pre-existing conditions from conditions that developed during quarantine. You also can't catch diseases that are obvious on close inspection but easy to miss with a casual look.

An experienced observer checking a new fish for 5-10 minutes can identify:

Active external parasite infestations (flashing within the first few minutes, excess mucus visible)
Existing wounds or ulcers
Physical abnormalities that suggest prior disease (healed ulcers, previous fin damage)
Behavioral indicators of disease (clamped fins, labored breathing, lethargy despite transport stress)
Gill appearance abnormalities (through brief netted examination)

Before the Fish Arrive: Setting Up Your Observation

Have your quarantine tank ready before fish arrive. This means:

Temperature matched to the water the fish are arriving in (within 2°C)
Aeration running
Test kit accessible
KoiQuanta app open and a new quarantine observation record created for the incoming fish

When fish arrive, take a water temperature reading from the transport bag. Before any acclimation, observe fish through the bag briefly. You can often see obvious abnormalities through the clear bag.

The Arrival Observation Checklist

1. Behavior During Acclimation

While you float the bag or container for temperature acclimation, observe:

Normal behavior:

Fish stays reasonably calm during transport (some stress movement is normal)
Fish rights itself if it tips (normal orientation is maintained)
Fish doesn't scrape against the bag sides

Abnormal behavior:

Continuous, repetitive rubbing against bag walls (significant flashing)
Lying on its side or tilting excessively
Rapid opercular (gill cover) movement out of proportion to activity level
Floating upside down or at odd angles

2. Body Condition

After releasing into the quarantine tank, observe body condition:

Look for:

Normal body depth for the variety (thin fish have a "knife-blade" profile when viewed from above)
Symmetrical body sides (asymmetry can indicate muscle wasting)
No obvious swelling or distension in the abdomen

Red flags:

Very thin body (suggests chronic disease, starvation, or heavy internal parasite load)
Obvious abdominal distension (possible ascites or constipation)
Asymmetrical body with one side significantly thinner

3. Skin and Scale Assessment

Observe the skin surface carefully with good lighting:

Look for:

Uniformity of scale surface (no missing scales, no obviously raised scales)
Coloration appropriate for the variety
No white spots, red areas, reddish hemorrhages, or opaque patches
No excess mucus visible as cloudiness or a slimy appearance
No visible parasites (anchor worm tails visible as white threads; fish lice visible as small flat oval creatures)

Red flags:

White spots (potential ich, carp pox, or excess mucus production)
Red spots or hemorrhagic areas (potential bacterial infection, parasite attachment)
Any ulcers or open wounds
Scale protrusion even in mild form
Visible external parasites

4. Fin Examination

Check all fins:

Dorsal fin: should be erect and undamaged
Pectoral fins: should be full and symmetrical
Tail fin: should be full with no splits, tears, or erosion
Fin edges: should be clean with no white fraying or reddening

Fin rot (bacterial), which presents as white or red fraying at fin edges, is common in fish from crowded holding conditions.

5. Gill Assessment (Brief Netted Examination)

This is the most critical assessment and also the most often skipped. Gill condition is where many diseases first manifest, and gill health is invisible without briefly lifting the opercular cover.

Carefully net the fish, briefly lift it from the water, and use a finger or cotton swab to gently lift one gill cover. Observe:

Normal: Bright red, full gill lamellae (individual gill filaments visible)

Abnormal:

Pale pink to white gills (suggesting anemia, severe bacterial infection, or severe fluke infestation)
Brown or dark gills (possible branchiomycosis or severe damage)
Obvious mucus or slime coating on gills
Missing or fused gill filaments
Any foreign material or visible parasites

Return the fish to water immediately after observation. Total out-of-water time should not exceed 20-30 seconds.

Should I do a skin scrape on new koi when they arrive?

Yes, if any abnormality is observed or if the source is unknown. A basic skin scrape from the lateral body and near the gill opening provides direct evidence of parasite presence. This is the most objective piece of information available at arrival.

6. Gill Movement Rate

After the fish has been in the quarantine tank for 15-20 minutes and has partially settled from transport stress, observe gill movement rate:

Normal gill movement: approximately 60-80 times per minute at 20°C
Elevated rate (100+ per minute in an unstressed fish): suggests gill irritation, oxygen stress, or disease

Count gill opercular movements for 30 seconds and multiply by 2. Compare to the normal range for your water temperature.

Recording the Arrival Assessment in KoiQuanta

Open a new fish profile and a quarantine record immediately for incoming fish. Log every observation from the arrival checklist. This creates your baseline record.

Anything unusual observed at arrival is documented as a pre-existing condition, which is important for two reasons: it prevents the quarantine protocol from being blamed for a condition the fish arrived with, and it establishes whether the condition improves, worsens, or resolves during quarantine.

The koi quarantine first 48 hours guide continues the protocol from where this arrival assessment ends.

Frequently Asked Questions

What should I observe when new koi arrive?

Observe six areas systematically: behavior during acclimation (flashing, abnormal posture), body condition (weight, symmetry, any distension), skin and scale surface (spots, wounds, parasites, excess mucus), fins (condition, any fraying or damage), gill appearance (briefly lift the gill cover to check color and condition), and gill movement rate after the fish has settled. Log everything you observe in KoiQuanta as the baseline record for the quarantine period. Anything unusual noted at arrival is a pre-existing finding, not a quarantine failure.

What health signs should I look for in new koi?

The most important health signs to check at arrival are: flashing behavior (rubbing against surfaces, indicating external parasite irritation), gill color (should be bright red; pale or dark gills indicate problems), skin surface condition (check for white spots, red areas, ulcers, or visible parasites), fin integrity (look for fraying, splits, or reddening of fin edges), body condition (appropriate weight and symmetrical body shape), and gill movement rate (count for 30 seconds and double). Abnormal findings in any of these areas should trigger a skin scrape for parasite investigation and adjustment of the quarantine protocol accordingly.

Should I do a skin scrape on new koi when they arrive?

Yes, especially if you observe any abnormality or if the fish comes from an unknown source. A skin scrape from the lateral body surface and near the gill opening identifies external parasites that may not be visible to the naked eye. Many fish appear healthy on visual inspection but carry significant parasite loads detectable by scrape. The scrape takes a few minutes, requires brief handling, and provides the most objective diagnostic information available at arrival. If the scrape reveals parasites, you can start appropriate treatment on day one rather than waiting for behavioral signs to develop.