Do you have Osage Orange (Hedge Apple or Bois d'arc) in your area? Very brushy and bushy limbs that are somewhat thorny and one of the hardest and rot resistant wood types around. Although horrible to work with, once your done you'll be proud you lived through the process of cutting it, hauling it, binding it, sinking it, and securing it.
Something that works well as fry cover is rolled up, wadded up hog wire. If you don't mind some "trash" in your pond. I prefer to stay as natural as possible, but sometimes man-made is very effective.
