On the back wall of my tank where the bubble stone releases its bubbles trailing up the wall, It seems to appear some tiny whitesh sacks. I can not get that great of a visual on them but it seems like little egg sacks or something. I thought at first they were snails or slugs, but the are immobile. Then I thought they might be turnicates. Small ones. I don't see them anywhere else in the tank yet, but I have been keeping my eye out for them. It's inconvenient that I do not have any pictures, but I do my best to describe.