Tenant moved out without notice room in my house. Do i owe dep. ?

[Laurie G. Zaslove]

I rented a room in my house with a month to month lease. The tenant paid prorated rent for Dec. 2018

He was only here for 1 week. Moved in Dec. 16th. I found a note on his bedroom door Dec 26th, 2018

He found a place closer to work. He paid rent til Dec. 31st. Since he did not give me any notice? Can i legally keep his security deposit of $150.? I am in Pensacola, Florida. thank you