I've heard conflicting reports from my two local shops. One said that dead rock can become live relatively quickly, thus drastically lowering costs. Another said that it is indeed possible, but can easily take over a year to work. I currently have about 25 lbs of live rock in a 40 gallon breeder, but i'd really like another ten to twenty pounds. However, it will be a relief to find out I could cut my costs in half and have a nice reef tank with 45-50 lbs rock with only half the cost for the remainder.