If this is the floating species Ceratopteris cornuta, it will do much better floating. When planted in the substrate it needs very good light and even then does not do as well. The other species (see the profile for info) can be floated too, but if planted will be better than C. cornuta. But if you acquired this plant (whatever species) as a floater, float it.I also picked up some water sprites! They were hard to find. Will they do best floating or can I root them in the fine sand substrate I have?