question about flood tray

Using suspended net pots in a flood tray

how much space should be between the flood tray and the bottom of the net pots? My guess is about 3 inches.

thanks in advance

to have enough room all the way through flowering, by the way

I've got a system that has 0 inches from the bottom of the pots to the tray. You can have any amount as long as the roots get wet during flooding. 3" is great. Of course the more space you have, the bigger your reservoir needs to be.