[header] How to pick a healthy gerbil that suits you [title] Observe the gerbils for a while. [step] Which seem active? Which seem happy? Look closely at the animals and see if they are generally perky. [title] Look for any symptoms. 
[step] Are their eyes open and bright? Make sure none of the gerbils have wounds, these are usually indicators of a past fight. Their coats shiny and well kept? A rough coat is usually a sign of illness.