I have shrimp in with my Bettas, Si and Willie (two 5 gallon planted tanks). Recently I posted about Willie lying on the bottom. He's over that, thank goodness.
However, I've noted an interesting behavior: I drop my shrimps' food in the same spot. Each time I do, Willie heads directly to the bottom and will lie on top of the food for about 30 seconds. Then he zooms away and continues his exploration of his territory.
Neither Betta bothers the shrimp although Si was quite curious about the new Assassin snails and pecked their shells a few times.
Anyway, thought Willie's need to lie on the food was an interesting behavior. I wonder if it's dominant or just fun.
BTW, here's Si and Willie. These were taken when they were about three months old. Both have darkened and Si's body is now so blue it's almost black (his "edging" is still the same) and Willie is a deep Silvery Copper.