over watering query

hi there, i have been looking over a few videos on youtube and come across heath robinsons perpetual cycle. i have a 4 pot wilma system with clay pebbles and was wondering is it possible to over water them as in the video heath has cut holes in the bottom of the pots to allow the roots to freely go into the reservoir. now i know i am no heath robinson but can someone explain to me how this works as i have over watered plants before but they were in soil and also not in a wilma.
does this make a difference because its a free flowing system?
here is the link to said video

[video=youtube;0m7B1S6fcVw]http://www.youtube.com/watch?v=0m7B1S6fcVw[/video]

any information would be great
thanks in advance

anyone? need to know asap. please help

RDWC, Recirculating Deep Water Culture...that's why the roots are in the tank(which is heavily aerated)...overwatering in soil = no oxygen for the roots, so it suffocates them

thank you massah. i think i will give this a go next time around as the ones i have going atm are looking fantastic. going to do the perpetual grow next time but monthly now 3 weekly, thanks for the reply