Sounds like the property has a lot of potential. It will be fun to explore won't it!
I don't have any experience with pond algae but there are some articles on the MDC website or try putting in something like "algae control" on google. This one mostly helps to id pond plants.
http://www.conservation.state.mo.us/nathis/plantpage/flora/wetplant/
The one below talks about control.

Here is a link that might be useful: algae control in lakes and ponds

i did see something very interesting the other afternoon, not that i think it will cure your algae, but it proves everything has a purpose. one hot afternoon this summer, i saw a very pregnant deer wading around in our pond, eating algae off top of the water, all i can figure is that it had nutrients that her body needed.as a funny afternote, our mare saw her too, and tried the same, from the way she shook her head, i dont think she liked it!

Try Barley Straw for your pond,,in the North they put it in early spring,,,Look on the web but it works great and not harmful to fish or pets

I remember reading in an old Organic Gardening magazine about using hay (straw, same thing isn't it?!!). I'll look through my old magazines & see if I can find it & post any information it gives.

I couldn't find the particular article I was thinking of but I did find one that you may be interested in. It was titled 'Watergardening the Natural Way' & was in the July/August 2001 issue of Organic Gardening. Here's the part you may be interested in:

KNOWING YOUR ALGAE:
Controlling algae is a key factor in maintaining your natural pond's balance, and the first thing to remember is that all algae are not created equal. Three basic types grow in ponds - surface algae, string algae, and suspended algae. Surface algae species, which stay very short and coat underwater surfaces, are very beneficial for pond life. String, or blanket, algae, however, grow into long filaments that can suffocate plants. Suspended aglae can overtake your pond and turn it pea-soup green when the water chemistry is out of balance. The accumulation of muck or sludge at the bottom of your pond can also contribute to unwanted algae.
In a balanced pond, sufficient oxygen and beneficial bacteria exist to convert waste as quickly as it becomes available so that toxic ammonia and nitrites do not build up. Enough plants live in the water to devour the converted nutrients. Symptoms of unbalanced water include that soupy pea-green appearance (called an algae bloom), which results from excess nutrients and sunlight. Adding submerged plants and beneficial bacteria or adding a shade source takes care of the problem,usually within a few weeks.

THE SECRET OF BARLEY:
North American pond-keepers are discovering the traditional, all-natural European technique of controlling algae by floating small bales of barley straw in their ponds. In the presence of oxygen and sunlight, the barley slowly decomposes, releasing minute levels of hydrogen peroxide, which prevent algae-but not other plants-from growing. One 8-ounce bale will treat 500 to 1500 gallons of water and, depending on the water temperature, will be effective within 2 to 8 weeks. Anchor the bale near the water inlet or base of a waterfall, where it will receive plenty of oxygen, and replace it every 5 to 6 months. (For sources of barley-straw bales, see www.organicgardening.com/library/straw.html.)

Here's some sites you may find helpful (if I link right!):

Organic Gardening site

Robyn's Pond Page

Pond Rushes

Copper Sulfate will certainly kill algae, but you need to be careful. Some fish species(trout-Koi) can be killed by copper based products. Kathy is right about Barley Straw and her directions are right on. You can also prevent algae by tinting the pond. Using pond dye limits the amount of sun reaching into the pond and reduces the potential for algae growth.

Here is a link that might be useful: Link to Pond Dye for Farm Ponds

I would avoid the copper sulfate. I suppose just putting in hydrogen peroxide would be way too expensive. It breaks down to water and oxygen.