This is going to come off as an extremely noobish question, but I seriously haven't heard mention of this anywhere.

For those really large enclosures (15'x10' or more for example), with more than 2 feet of soil mix for digging, how exactly is the substrate cleaned? Do you ever actually replace all of that substrate, or just spot clean as you see a mess? I mean surely there is liquid waste, so do you have worms in there to take care of it or do you just buy massive amounts of soil frequently?

Thanks!