Their spines are bent and they have very short bodies..often have swimming issues and die quickly.
IMHO the larger cories are not a good choice for a 20 gal high. The orange laser is a color variation of the emerald, which means it will easily rach 3". They are ideally kept in groups of 4-6, and they are very active. A julii cory however, at max size 1.5", would be a fine choice for a 20 high.