Auto pot help

Any tips on auto pots would be appreciated what way does the copper mat go down to ?

What tips are you looking for?

Have a 3mx1.5mx2m tent thinking 18 was to many to put in there I have 15 litre pots with 4 600 w lights over them

18 might be much 9 would be good...are you hand watering or using a feed system?, hand watering 18 will and moving them around will quickly become a pain in the ass ..but thats just me..I do small grows for personal