Riccia fluitans (Crystalwort moss)

or is it Vesicularia dubyana? I had some of this prolific stuff and it comes to mind
when I hear the discussion of attaching Java moss with strings. This stuff you could
just shove in the gravel or leave it grow. It got everywhere rather than staying in
a confined shape that would have enhanced the aquarium's looks. I'd like to discover
a small plant that would carpet the bottom but that wouldn't wind itself among
all the taller plants. I think that rules out the moss types. What do y'all use for this?
Any preferences or complaints?