Place netted barley straw, a quarter pound per 100 gallons of water, in your pond in very early spring. Placing it in the water too late will not help keep water clear.
Rake or scoop any visible algae out of the pool. Not only is it unsightly, but under the right conditions it can kill your fish.
Replenish your barley straw in mid-July, as the first dose will have completely rotted away by this time.
Vacuum the bottom of the pond in late fall when you remove the fish for the winter, or before they become dormant in a warmer climate. Removing mud and debris will greatly improve clarity.