I vote for the bermuda grass but at a 45 degree angle you are most likely going to have a difficult time with anything. You may end up with cutbank erosion. I would think that if you use rocks you are going to have problems with them tumbling down into the depths. A 12' depth for a 1/2 acre pond is very disproportionate in design because the slope is very dramatic. My calculation is the distance from bank to bottom is only 83 feet and that's with a perfect circle. That's quite a hole. You might want to consider reducing the slope a bit rather than spend a lot of money on rocks. Also, with this depth to area ratio, you will most likely need to aerate the pond because of the stratification that will occur. The statification will cause an oxygen problem in the future and be difficult for the fish. Since you just finished construction late this past summer, see if you can stabilize the bank with bermuda grass first next spring and if this fails you may have to consider reconstructing the bank. Otherwise you will probably be battling erosion problems for years. Maybe rocks will work where you are but down here in Louisiana we don't have rocks so it's really not an option anyway.
