If you have algae & real plants,
this pinned topic might help you sort out the root of the problem. Adding a fish to try and help, will often not help. Especially not hair algae.
Can you give us some more information about your tank?
How long has it been set up?
How many gallons is it?
What fish do you currently have in it?
How long have you had the hair algae problem?
Do you have real plants in your tank? And is the hair algae only affecting them?