Ricordeidae vs. Actinodiscidae and others
These families and their genera (ricordia vs actinodiscus, discosoma and rhodactis) can generally be separated by looking at a few characteristics: verrucae (the protrusions on the oral disc-charateristically bulbous and bicolored in Ricordia); the stalk (almost non-existent in ricordia); the texture (discosoma is soft, ricordia, firm).
Best thing to look at is the verrucae. There are discosoma that look like ricordia, but the surface protrusions are little tentacles, and are not like ricordias bubbled protrustions.
I agree with the above: check out the corallimorpharians forum for better help. Morphological taxonomy is dubious.