Each Ecosphere contains small shrimps (8 10 in a medium), filtered seawater, algae, gorgonian & gravel which are all part of the working closed Ecosystem. All the surfaces act as hiding areas for the shrimp where micro-organisms can also attach themselves. The gorgonian (branch) is a non-living material & is hand cut for each individual Ecosphere. Therefore, no two Ecospheres are alike, making them truly unique gifts.