hello there, i have a spare 30g tank and i was planing on doing my first planed tank so i could use this as a practice :)
I have been looking at planted tanks with potting mix on the bottom and gravel over it.

My question is can you use potting mix then sand? or does it have to be gravel so the nutrients can get into the soil as im not sure weather fish waste and such could get through the sand?

cheers :)