Best substrate for planted tank

[RJIESQ]

What type of substrates does Seachem use in its show tanks?

I used eco-complete and was told that this produce is a waste of money and that I should have a good clay-based substrate. Of course, I hear this after the tank is set up.

Everything is working fine, and growing well. But I am just concerned regarding sustainability over time.

This outfit I spoke to indicates the roots are the only way to feed the plants, offering fert-pellets. They do no put much stock in the foliar feeding, as is the case with Seachme product.

And is it start to heat the substrate?

Interested to know your thoughts.