Hey Kyle...too bad I didn't see this earlier.....By the pointed carapace, small under-turned claws and algal growth on the shell...My best guess would be that the sewers of Windsor are now home to one of the smaller species of decorator crabs. Many of the larger ones show up in stores but they are pretty sketchy as far as "reef safe" goes since they will cut pieces of sponges, polyps etc to grow on them. The small ones usually just "decorate" with algae.
Do you have any millepora sp. in your tank that were wild collected or maricultured? If so, look for some pics of a gracilis decorator they live in them/clean them in exchange for a protected place to live...not sure but not likely harmful to most corals other than stealing food from LPS like any cleaner shrimp.
Too many limbs and fully developed eye stalks to be a pycnogonid sp. Just my $.02