You cannot ask your employees to stay totally off social media, the only extent you can go is to ask them to curb the use during office hours. It’s even possible that you recruited these talents from LinkedIn, Facebook or Twitter.
What you should do is to put in place a clear social media policy in order to ensure it is used appropriately, outside of office environment, and limit use during working hours. To serve as a guide for drafting your social media policy, gather input from your current employees. As for the tone of the policy, don’t adopt a restrictive approach and not focus on disciplinary actions for misconduct.
State clearly in the policy guide of being mindfulness of the company’s reputation when acting on behalf of the company on social media. If they also mention that they work at your organization, there should always be a disclaimer that opinion expressed is theirs and not the company.
When acting on behalf of the company on social media, a good thought should go into every post. How it could hurt or affect the company should be a top priority. Utmost respect should be given to intellectual properties of others, every source should be credited.