If they are really grass carp they eat plant material like submerged water plants. If you have excessive weeds in your pond they are a good thing or if you pond is in balance with weeds they may be the reason you do not have excessive weeds. So they CAN be a good thing.

If they happen to be regular carp (are you sure of the identification?) they are taking up carrying capacity of the pond for a fish that most people do not consider desirable. So for most people would be a negative. A few people do keep regular carp in ponds on purpose, but very few.

Regular carp can be introduced to ponds by accident. For example poorly sorted stocking minnows might have off species. Or if a pond is in a flood plane flood waters can introduce them.

Last edited by snrub; 04/09/14 09:17 PM.
John

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