Ricci Grass

Riccia is not a grass. It is a plant without roots that either floats or sinks in my tank.

I have had limited success tying it to a rock - it eventually grows and shades the lower part that is tied and that part browns and it lifts off when pearling and you are back to tying it down again. A hair net can work although I have gone to an unfolded shower scrubby sponge thingie - the key is to get something not much bigger than your rock because again when it pearls the riccia lifts up and makes a hairnet ballon inside the tank.

All in all it is troublesome. It can attach itself onto dwarf hairgrass. No matter what, it needs frequent trimming.

I've found it to be an easy plant to grow on a rock. As stated above, the key to success is to tie it down tightly(it would be difficult to tie it too tightly) and keep it trimmed short to allow light to get to the majority of it.
Pick up a small, fine hair net at your pharmacy. It will have an elasticized opening. Lay the pad of riccia over the rock(a flat rock is best) and wrap the hairnet over it so that the elasticized opening is on the bottom of the rock and tie it off tight with fishing line. Then wrap it tightly round and round with more fishing line and tie that off and you're good to go.
The riccia will grow through the fine holes in the netting and hide it and the extra fishing line in a short time with good light. A really short time if you also have CO2. With these two elements it will pearl like crazy and be beautiful. It will need regular 'haircuts' depending on the speed at which it grows, to keep it short. By short I mean maybe between 1/4 and 1/2" outside the net. Just reach into the tank with a small sharp pair of scissors and trim it up. Just be careful not to snip the netting in the process.
Trimmed off pieces will then float to the surface where you can leave them to form more pads for future use or take a fish net and scoop them out.

Len

i've managed to cultivate algae on my rocks that looks like thin grass. its a pain keeping it off the plants but it adds to the look. besides, it's fun cleaning it off and trimming it every couple of days.