However, you could use some creative options:
* A shoal of carps (since they often swim in groups)
* A school of carps (also used for fish in groups)
* A swarm of carps (if they are moving in a dense, swirling group)
* A pod of carps (used for some aquatic animals in groups)
* A gaggle of carps (a playful, humorous option)
Ultimately, the best option depends on the context and the specific action of the carps.