My three pacu do the same thing, eat all the wafers. What I sometimes do is hand deliver some wafers to the pleco cave. The pacu's are too big to fit in, though they do try. Does not matter day or night, the pacus will get those wafers and anything else if you drop it in. I'll also feed my pleco zucchini and cucumber, the pacu's might nibble but it's too big for them to take it all in, so the pleco gets to eat.