I only use sand.Is it ok to only use sand as a substrate or would I also need to use soil under the sand?
I haven't purchased anything yet I'm just doing some research first. What is a good light colored semi fine substrate that would work for a lightly planted tank?In my opinion, it's unfortunate that you purchased powersand. If anything, it's a secondary addition. I would have just gotten Aquasoil by itself. Since you already have it, I would use it in addition to aquasoil.
Powersand doesn't contain many nutrients, so while you can plant directly into it, you'll still have to dose into the water column.