These are great plants to have in the fish pond area. In spring they are incredible with their bright blue flowers and tall slender leaves. After they flower the leaves stay nearly perfect for the year. They really do add a realistic look to a Man Made Garden Pond. Do not be afraid to kind of over use it. I have some in pails in the waters as well. They should not be completely submerged. However you can submerge them maybe an inch at most . Your fish will lay eggs in the pail as well if they can, which is really cool. Add a rock or two to the top to make them bottom heavy. Otherwise first good wind and they are toppled over. If you like, add other small water pond plants in the pail with them. it adds extra interest. In time Moss will grow over the soil and give it an unique look.
Hint Here: When planting out side the pond remember that the soil is dry, they like wet. To fix it just throw a bucket of water on them a couple times a week. Another hint for general pot planting in the pond is never use bricks. They will disintegrate in the water with in a few years. Use rocks, they are more interesting anyway. Also make sure there is a hole in the pail. This to insure water can get in if the water level becomes low in the pond.