Gregory Day
Member
which would be the best base layer to use tank is 8x5ft. I will use sand on top also how much would I need
That's true @Filip Krupa, and you've got some really great growth. But it just makes good horticultural sense to feed plants through both leaves and roots. And I think on the whole plants tend to do a bit better if they're planted in a soil substrate as well. There are other benefits to using soil, like providing a buffer against mistakes such as missed fertz doses. And I think perhaps soil also encourages increased microbial activity that can help to mature and stabilise a tank biologically and in a shorter period.
So personally, even though you can theoretically grow plants in marbles alone, I'd always use a soil substrate of some description, whether that's plain old dirt or Gucci substrate like ADA AS.