yes you can but it would be a pico reef system. I would probably get a tank about 80-90L if you want a small system and are just starting out in marine. The reason is picos can be quite demanding in that they require a lot of maintainance due to the very small quantity of water. Marine systems require almost perfect water conditions to be successful and a large tank has more buffering capacity and is generally more forgiving with errors. Saying all that picos are doable and if you look around on this forum you will see some absolutely spectacular examples of what is possible.
Kindest regards
Joe