Greetings, pond pros!
Here's my situation - I live just south of downtown Austin, TX and happen to own a lot that extends halfway across a spring-fed creek running through the hood. The creek is empties in a large bowl directly behind my house creating a sort of swimming hole for the locals kids and a fishing spot for some. It's roughly 50 ft in diameter ranging from ledges at 1-3 ft deep to a large channel down the middle at 8 ft.
At any rate, like most creeks around this part of the country, it's cut into limestone and is real perty when the water is flowin'- in fact, during some periods of consistent rain i've seen some pretty decent fish swimming about and can see about 6 ft deep.

During the summer months and periods of little rain, the whole thing can get a bit funky - a light film on the surface, murky - and the spring although constantly running, isn't creating enough motion or displacing enough water to get good oxygen flow. The other aspect is that a few culverts drain into this so any random gunk on the roads will wash in it- not to worried about consuming the water or anything living in it - just want to have a nice habitat for fish and other wildlife.

I'm considering adding an aeration system and am looking for advice. Any special considerations to take regarding it being a creek vs a pond, limestone vs whatever, urban runoff, city ordinances ;-)
the fact that our summers can easily have 100+ degree days for weeks on end and no rain.

Here is a video I took of the creek after a pretty heavy rain - http://www.youtube.com/watch?v=kUnicIvfsPQ

and here is a pic of it's normal state - (this shows about half of it (I know, bad pic)
http://picasaweb.google.com/lh/photo/bOiqOJgK8utk42BQ3FiLQe6oA-DpZt85AeUuGM6xyTo?feat=directlink

Whew! Thanks for listening...