The raft system as detailed by Chris is economical. I also find Coastview miniature AP system quite useful.
I intend to join the Media group too because my system is combo -1st part Media and 2nd part Raft system. The media section help to reduce the cost of filtration of the Raft system.
I prefer the word efficient over economical because an efficient operation is economical and more. My big system is a small scale commercial system. I am applying what I have learned to a very LARGE farm. I have 1000' of growing space and the new farm will have about 10,000' of growing space when done next year.