Your lake sounds rather shallow at 5-8'. Also Working against you is going to be the water temperature during the summers due to your location and the depth. This creates a less than stable eco environment.
I have a suggestion I hope you try before next summer. Contact a good experienced Biologist (See one link below) and get their advice after a complete testing of the lake water, well water, soil in the lake bed and soil in the run off area.
There very effective ways to control algae without spending the money for aerating a 30 acre lake. Find out all the facts before you throw money at it.
http://aquahabitat.com/pondering.html http://www.dirtdoctor.com/view_question.php?id=761&set_theme=1 Scroll down to the Corn Meal section at the above link for more information.
I am familiar with your dead water concept. I have two ponds on my property that would fall into that category that I do not have any problems with thanks to some initial testing and corrective steps.
One extreme example of dead water is at Green lakes state park near Syracuse N.Y. Plunge pools from glaciers left lakes that were up to 80' deep. There is practically no turn over of water from the bottom of the pools and there is virtually no significant aquatic life in them due to the lack of dissolved oxygen.
Algae is not all bad all the time.
Good luck
JW
