Cryptocoryne (crypt) is the substrate-rooted aquatic plant genus dominated in the hobby by C. wendtii (green, brown, red, tropica), C. beckettii, C. parva (smallest hobby crypt), C. balansae (largest), C. spiralis, C. lutea, and C. undulata. All thrive at moderate light (50-100 PAR) with or without CO2.
Notorious for "crypt melt" - sudden loss of all leaves when moved or exposed to parameter changes. The rhizome/root mass survives and regenerates submerged-form leaves over 4-6 weeks. Expected behavior, not a death sentence.