Raiders are believed to have jumped over a fence in Clare to steal between 40 and 60 valuable koi carp from a pond.
It is believed the colourful fish, which are generally kept in outdoor ponds or water gardens, are worth a total of £4,000.
The theft took place at a home in Bridewell Street, Clare sometime overnight between Saturday, January 11 and Sunday, January 12.
Polie are now appealing for anyone who saw anything suspicious at the time, or has been offered koi carp for sale since, to share details with police.
Anyone with information should call police on 101 or email Sally Brash, quoting reference 37/2724/20.
People can also report incidents online by visiting the Suffolk Constabulary website.
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