Distichodus Affinis

Hey folks

Has anyone had experience with keeping Distichodus Affinis? My dad has had 2 of them for the past 10 years. They seem to be like little water pigs .They love lettuce, spinach, cucumber in particular. One other interesting thing I notice is that they flip over for an hour or two after water changes. They've been doing this since he got them 10 years ago. We used to be worried initially but nothing serious ever happened so we got used to it. Anyway just checking if anyone else has/had these odd fish.