I often find things that surprise me in my tank. I ordered rock and sand from, I believe, Tampa Bay Saltwater and that has added a large amount of life into my tank. Sometimes it is a neat sponge or a new invert running around. I even had a few surprise corals. This morning I found a crab under a rock filter feeding. That was new! My tank has been running for 8 or 9 months now and I love finding new surprises still. Here is a terrible photo of my new crab friend! He hid pretty well under a rock once I saw him.