this is my feeling too. it's all population.
if you have thousands, theres something for thousands to eat. overfeeding, or too large substrate or something. i have two and i cant seem to get them to make kids...
of course i feed once a day only as much as the fish eat in a couple of minutes. barely anything makes it too the bottom and what does is eaten by shrimp and the snails. in fact... my shrimp have taken to swimming up and floating upside down to eat like the fish from the surface i have some pics i should put them in my gallery.