Sea Hare advice

[Winters]

Hello! Anyone have any advice on putting in a Sea Hare (or "Sea Slug") into an aquarium for removal of hair algae? I have a fair bit in my (4 month old now) 90g on the rocks and glass. (No other livestock except for snails and hermits) Will this be a good idea, or will the poor thing starve once it's eaten all there is?

Or.. anyone willing to lend me a Sea Hare?? AI has a couple for twenty something dollars.

Thanks!