With 2.2Wpg you should be able to grow it no probs.
You can either float it or tie it to slate or rocks with fine fishing line or fine hair nets.
It has been said that Riccia likes allot of nitrogen phosphorous and potassiam, but my experiance with riccia have been grown with SERA and NutraFin PlantGrow liquid fertilizers with very good effects.
Regards,
Graeme.
Forgot to mention that Riccia likes plenty of Co2 if grown submerged!!