I just noticed that one of my larger cherry shrimp has problems swimming. Its back (smaller) legs are propelling it fine but it has trouble staying up the correct way. Therefore, it cannot direct itself and gets pecked by the fish. Is this a sign of problems in the tank or is this just an ill shrimp. I've QT'd it at the minute waiting your replies. I did notice the other day that one shrimp had died during the night as when the lights came on the Harlequins had a ruck for the flesh. Any ideas?