Thanks for comments.
Stepheus, that's good idea with sand.
I'll try fill with sand between rocks something like river, and maybe ad some moss on small rocks.
It's running for about 4 weeks now.
Lonepeace, maintenance is very simple. Every 2 weeks i change 1 liter of water and that's all about mainteance. It is completely algae free.
This is how it looks like before (11/2006 - 05/2007):