Advice needed for new aquarium with potting soil substrate and...
 

Most potting soils contain fertilizers which are great for plants, but
very harmful to fish. I would get rid of the potting soil altogether
and use a sand or gravel base, especially since you want to keep fish in
there too. Remember to use an aquatic plant fertilizer (read label to
make sure it is safe for fish) once a week and don't vacuum the gravel
around the plants to thoroughly.

Can I grow my plants in just sand? Don't I need some kind of soil??

Advice needed for new aquarium with potting soil substrate and...
 

Can I grow my plants in just sand? Don't I need some kind of soil??

Most, if not all plants will grow in rocks, they may need liquid
fertilization, but not potting soil, or soil persay...

much has been done with pure soil, meaning, no other chemicals added, just
dirt... and many horror stories have been brought here with "Help, my fish
are dying, and I dont' know why" as the subject... they were all using the
wrong soil, or something similar...