I'm w/Doug, Great deals are only great if you need the item, unless the rock you have is very dense (not porous enough to house ample bacteria for bio-filtration) or you want to scape the tank some more or you plan on upgrading within the next year to a larger tank, it would be overkill. If you want to take advantage of the deal and you have some Christmas money burning a hole in your pocket. then cook in a trash can and enjoy. Remember it's not the quantity of the rock it's the quality and sometimes more rock is simply more rock you don't need. Fish need room to swim, coral need room to grow and the more rock you have the less water volume you have for these. Good luck