thank you all, I think, no I'm sure I have decided that it is indeed a waste of money.
one good reason for not using it for me was: if there are wires underneath the substrate, the plants will grow their roots around them. and if ever you want to take a plant out, the chances of taking up the wire....
no heating for the substrate it is.
THanks again.
I wish I had a decade ago:swear:
I'm still mad, hehe.
They cost 300-700$ then too.
**** that Dupla!
Regards,
Tom barr