Last night I decided to stay up later than normal. I've been very curious what critters lurk in my 75g tank after the lights go out. I did not see anything that I think would cause any problems, but did see a lots of bristle worms, amphipods, copepods but what surprised me was a huge amount of mini brittle starfish! I have no idea where they came from. Normally I would think "hitch hiker" but I have add anything new to the tank in about 4 months. Is it possible that I have missed seeing them in the past. There are a lot of them. I stopped counting after 30. I'm sure yhere would be more in the substrate that I couldn't see. It's my understanding these little guys will help clean the tank. Not in a big way but they hurt nothing.