Smaller pieces for smaller aquariums. The average size is 2-4 inches. Live Rock is an absolute necessity for all saltwater aquariums. They're living filters that will increase your success of keeping marine life ten fold over tanks that don't have it.PRE-CURED and HAND-PICKED LIVEROCK Saltwaterfish.com offers the very best "Pre-cured" Nano Live Rock. Each piece that is shipped to our customers is hand-picked for size and coralline coverage.In our Live Rock Curing System the rock is scrubbed down and power sprayed to remove debris. The rock is then placed on shelves where it is sprayed down with saltwater in order to allow many of the unwanted "pests" to crawl into the tanks below.Once you receive your rock, you must re-cure the rock for at least a week. During shipping some of the beneficial bacteria will die off. Do not add this directly to an existing tank!IMPROVES WATER QUALITY AND IT'S BEAUTIFUL There are a number of reasons why our nano Rock has become so popular in the aquarium trade. Most importantly, it's a natural filtration device which aids in allowing an enclosed aquarium system to flourish. It's also porous, lightweight, and comes in excellent shapes, which will give your tank a natural look for both you and your aquarium inhabitants. The porous surface and crevices of Rock causes it to have an increased surface area, which results in great places for all micro and macro life, like beneficial bacteria and copepods, to flourish and multiply. And on top of all that it looks great too! Nano Rocks are also usually covered with coralline algae--a hard encrusting algae that comes in colors of green, purple, blue, and pink. Plus, Live Rock will often times have coral skeletons and other mineral deposits that are conducive to keeping marine life.Note: The weight listed is the total weight including packaging.