Mkonge Hotel is not the smartest hotel in Tanga but it's peaceful and spacious with decent-sized rooms, clean sheets and working AC. The food and service are nothing to write home about; you'd do better to eat elsewhere.
By far the best feature of this hotel is the lovely spacious grounds where you can sit and enjoy a cold evening drink while watching the boats pottering around in the bay. Very relaxing and tranquil.
A room here cost me around $30 for the night.