My Blue Dream Cherry Shrimp recently arrived and my tank at least seemed all ready to house the shrimp. I had a seeded sponge filter along with Tetra Safestart, and I acclimated the shrimp for 1h and 30 mins. After putting them into the tank, some of them went to the filter and some of them hid in the rocks, but most of them were just swimming around in the water. After a while when I came back, all of them except for one or two shrimp were under a rock or filter. Is this normal behavior, and should I be concerned?