The Crytocoryne lucens is one of the larger plants of the Cryptocoryne family. It's growth rate is slow though so will only get to about 20cm tall which is fairly tall for a Cryptocoryne.
It requires a water temperature of about 22-28C and enjoys a high light environment.
Understanding Crypt melt - all Cryptocoryne species require stable water parameter and light conditions. Once planted, Crypts should not be moved otherwise it can trigger what is called Crypt melt. If a Crypt has a significant change of environment (ph, kh , gh, lighting intensity or duration, root disturbance etc), Crypt melt can be triggered. The leaves start to disintegrate as the plant prepares for its new environment - DO NOT WORRY! Your plant will begin to grow back over the next 30 days (sometimes sooner, sometimes later) - it's still very much alive and busy getting ready for the growth of new leaves. In the meantime, any decaying leaves should be trimmed and recycled in a compost bin.