Mark- You are correct. It's Crypt Parva. First time I've tried it. Very slow growing, and loves the light.
Steve- Cladophora, is a slow growing form of algae. In it's natural environment of rivers and streams, it creates the 'ball' effect by rolling around on the river bed. They can grow as big as a football if left, and in actual fact, they're hollow inside.
Flattening it out, and weighting it down will create in 'instant' look. Certainly wont get out of control. I was looking for an alternative to moss, yet create the same look/colour. obviously texture is drastically different. Moss can sometimes have you running circles around it...