We’ve made the decision to add a non-native species to the pond: grass carp. Originally from Asia where they are used to get rid of weeds in paddy fields and that is what we need them for here. We have the first signs of broadleaved pondweed in the pond and really do not want it to take hold as it could completely take over, as it has done in the small pond.
The fish are herbivores and won’t eat amphibia or other fish, and won’t breed either and so are a safe and hopefully effective form of weed control. So long as the herons don’t eat them.
