In that bare tank I'm not surprised, at 5 inches in nature, dovii are vulnerable to many predators (birds, reptiles, otters etc etc) and hide under hanging vegatative cover, under branches, logs and such.
That tank doesn't offer any such security that aa dovii instinctually searches out.
I also agree about pellet size.
In a number of studies the main stomach content for dovii in nature, are insects.
I live in very near dovii country and can tell you large numbers of beetles, grasshoppers and other insects are constantly floundering and disturbing the waters surface, and picked off by large cichlids.
