want to put in a fountain and keep it indoors for the winter. the place is afternoon sun.
If you keep it in container with a soilless media then this can be possible to keep the container in your fountain. Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soilless-growing-mediums.htm
https://www.gardeningknowhow.com/ornamental/foliage/corkscrew-rush/growing-corkscrew-rush.htm