Karen, I ordered the pots from Drs. Foster and Smith
http://www.drsfostersmith.com/...
The bottoms actually are more pointed when filled with soil and you can vary the depth they float by adding pea gravel to the top. The roots grow out so you get good filtration of the water through them. The water celery has grown out of the basket on top and now is floating with roots around the basket. Just what I want, coverage and more filtration of the water. I attach lead sinkers (1/4# at the lightest with fish line to keep them in one spot (more or less - in a good breeze they will drag that weight across the pond bottom since I have little gravel on the bottom)). I am quite happy with them and will order a few more next year. They wouldn't work for water lilies that have to have the plant lower in the water. I have used pea gravel before but in the last few years they haven't grown very well - water lilies that is. I put tabs in them but still not much luck. And this year has been stupendously warm and sunny - hot even in the 70-80 range.