You know the Riccia, the plant for aquariums?
In the network if they are different ... but I think this article on a U.S. site is simple, with many pictures and understandable.
He speaks of the absolute best way to fix Riccia, known floating plants, rocks, stones, wood and especially, better food.
This particular map, put on so many pebbles, can create beautiful layouts in the aquarium ... patches of light green color with the co2 in the evening we offer a nice "perlage".

Having tried this method, I can say it is not easy ... but it works.
We must do first of all attention to firmly attach the retina behind the rock, not trovarsela to turn down the stream in the aquarium!
Then remember to cut regularly Riccia, otherwise it is growing too easy for the part below, closer to the rock, rot, and then face off over what is grown.

Caution, this is still a plant Riccia define "weed". When cut / crop it to just remove the individual from the water rocks is very convenient not to be with many pieces of Riccia fluitans that "fluitans-ano" in the aquarium ... nestling in any crevice useful and, if exposed to light, also increasing where there should not have ...