I haven't added much to the tank lately, and it's been a long time since I've seen any hitch hikers, since the tank is well established and the usual stuff ran its course.

I noticed this little thing growing months ago, and figured it would either die or grow. It didn't. A month ago I snapped a pic, and another one tonight. It may have grown a tiny bit, but it's been in the same spot for a long time. Nothing is bothered by it, I'm just wondering what it might be.

Any ideas?