If you decide to use a shrimp... this is how I cycled my 6g.
Added live sand, live rock, salt water, heater, powerhead, etc. Waited about a hour and added a shrimp. That's about it other than testing, adding top off water and waiting... pretty easy.
I tested the ammonia, nitrites, nitrates weekly. After you ammonia and nitrites go to 0 and your nitrates go to up... cycle is done.
Wait until after the cycle to add anything including inverts. After the cycle you can start adding the fish and cleanup slowly. Your 29g should be able to house several different inverts including a serpent star.
Good luck,