You should run an AI for both on cycle and PCT. Aromasin is preferred, but Arimidex will work as well.
On cycle: 12.5mg EOD Aromasin, or .5mg EOD of Arimidex.
PCT: Aromasin 25/25/12.5/12.5
Edit to add: Even though you are running a really low dose of Deca, it would be a good idea to have some caber on hand just in case.