Plantrivia

#6 is a Crinum species, probably C. americanum, which is found in the southeastern states.
#5 looks like a Utricularia species (bladderwort)
#4 could be a Ludwigia species
#2 has leaves like Ceratopteris, but it is a stem plant, whereas Ceratopteris is a crown plant. Ceratopteris is a fern, but I bet #2 is a flowering plant. It looks like it is adapted to submersed or emersed growth. This could be an interesting aquarium plant.

Yup! #5 is a bladderwort. You can see the little bladders on the leaves.

I think that some or most of the bladderworts do not produce roots. They are like Ceratophyllum in that respect. I would weight the stems down on the gravel with some small pebbles, but would not expect them to root.