Hey, Tampa,
Looked at the pics of your pond. really nice!
Don't be too concerned about the algae on your falls rocks. Got the same type as you and can't keep mine free. It's a form of 'string algae' and is one of the toughest types of algae to eliminate or even hold in check. There is a product out that's called S.O.B.(String Algae Buster) that has worked well for me. You have to use it exactly as directed or it's not too effective. Won't harm your turt or any fish you might have. I haven't seen it in pet stores, just in garden shops that cater to the pond crowd.
I have all 11 fish downstairs in the 265 gallon pond. Also are 4 round, underwater containers packed with anachris, 1 with a tuber of Helvola Lillies and 2-10 inch square underwater containers with good growths of lillies. My light on a timer is a 160 watt turtle UVA/UVB light that is hanging off the floor joists,aimed down on the pond in general. On one of the ledges are 2 square containers , one full of Blue Rushes and one with 4 stalks of cattails. All are growing nicely and the fish are lovin' all that plant life. George