Alchimia Grow Shop
There's no problem using 3 plants per slab, hydroponic systems need smaller pots than organics. If you make a SOG, you can even put 4-5 plants per slab. The more plants yo have, the more waterings needed, for the slab will get dry much faster than with less plants.
You have excellent info on hydroponic irrigation in this post .
Thanks for your confidence,