Koi and goldfish are controlled exotic fish species (see ARM 12.6.2203). They can be legally kept indoors in an aquarium or outdoors in ponds that meet the following criteria:
- not larger than 400 sq. ft.
- not within 100 year flood plain
- 200 yards from open water
- does not receive diverted surface water
- does not discharge to surface water
Such ponds do not require stocking permits for koi or goldfish; however, they are required to be registered with Montana Fish, Wildlife and Parks. For stocking of other fish species in ponds please contact your local Fish, Wildlife and Parks office.
To register your koi or goldfish pond please answer the following questions and press submit.
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