I wouldn't bother with this.
Pond pumps don't use huge amounts of power (25W?).
Unless you live in a very windy site and mount the turbine up on the house, it isn't going to generate much power, plus what happens when the wind stops? - answer, you need a rechargeable battery as part of the overall system. Yet more complication to deal with.
Those fish aren't going to too impressed on calm days othereise.