I'm thinking of using only live rock (in 29 Bio- cube) adding 10-12#'s a week ' till I reach 40#' s or so.
Any problems with this plan?
Extended cycle?
Possible algae problems?
If this will work - should I add any snails during this process?
You can add rock gradually. Be prepared in case you see a mini cycle. Have water ready to do a water change. Not everyone can afford all their rock at one time, so what you want to do is very common. :)