I have recently planted 3 small Corkscrew Vallisneria plants directly in the PFS (so sand/gravel, I think). Tonight, I learned this is a Rosette plant my thank you, to Lady Hobbs.

The tank light is a T5 light, giving out 42 watts, total.

At first, it was difficult to keep the Vallisneria rooted. I had previously read that this type of plant needs to have the crown (where roots meet stem, I learned) exposed. I did this and did finally get them to stay in the PFS, but am now wondering if they get everything they need to thrive from it.

My first question is: Do I need to re-plant these in a different substrate?
Second question: Do I need to feed these plants any type of fertilizer?

Thank you for any information you can share.