A week ago I put two amanos in my 125 gallon, they would wildly swim around and explore or eat, now they've anchored themselves to a rock out of sight and haven't moved much. I've done quite a bit of research on these little guys after they stopped moving, some say they are social and need large groups to feel secure. They still have their original color so I don't think they are ill. Twitching pleopods are said to be a sign of certain doom but they aren't twitching per se, more of a back and forth motion while the front legs are cleaning them. Water parameters are good with nitrates only at 5ppm, co2 isn't hurting any other fish and my ph hovers around 7 when the co2 is on. Also no predatory fish in the tank, just cory cats, platy fish, neon and glow light tetras and a couple of crackhead danios. Any thoughts?