Hi Merdav,
Since the turbidity in your pond is caused by a heavy plankton bloom, I don't think barley or any chemicals will help clear the water. If you can prevent fertilizer and organic material (leaves, lawn clippings, runoff from livestock)from getting into the pond, it will eventually become less fertile, and begin to clear up on its own.
If a self-sustaining fish population is a goal, around 30" give or take is a good compromise between fish visibility and food chain.
