Grizz, you are right to think about O2 loss in the hot months. The risk is something called "turnover," when the water becomes oxygen depleted below the top few inches, the fish all migrate to those few inches, then a hard summer storm suddenly cools that water and it sinks, leaving the fish in oxygen-depleted water. I'm sure you're wandering around the aeration section of the Boss, and have figured out that a bottom aeration system is a lot more effective at maintaining the health of the water column than a fountain on the top of the water.
I've found an interesting and seemingly effective piece of pond management to be the use of beneficial microbes, which are available from a variety of suppliers. they chomp up lots of nutrient-producing organics (think what fish do after they eat, etc., but also decaying leaves, etc.), and so make those nutrients unavailable for algae growth.
For us, the most important thing is--the dock. Being beside the water is just different from being out over it. The next most important thing, if you have some hill on one side of the pond, is a waterfall; the addition of sound and movement really adds another dimension.
From a landscaping perspective, I think that water iris are a wonderful way to integrate the pond into the landscape--the foliage is good many months a year, and the flowers and reflections are terrific. Look into Louisiana iris as well as the yellow, blue, and white flag which are more common. Amazingly enough, Lowe's, at least here in Ohio, is a great source of marginal plants for ponds. Don't be afraid to experiment with plants, water lilies, etc., any and all of which can be exterminated if they go wild (but no duckweed, IMHO, and definitely no lotus in an earthen pond).
As the above may imply, Tarpondriver is right about the pond's coming to dominate your consciousness, as well as your landscape. In part because water is so wonderful to have, but also, at least for me, because the pond changes not only with the seasons and the months, but can change in an hour or a day or a minute, and hosts a complete biology in its banks. Have a great time!!
