They will reproduce and there are many species of them. If you bought live rock you definitely have them. You can also buy live pods
from reefs2go.com. You should have refugium and an established tank before you get a mandarin. I had my 90gal setup for 6 years. 2years with refugium. My mandarin is a year in my tank this June. He also eats frozen which is easential to long term survival. They hunt about 18 hours a day and eat hundreds of pods
a day. You need a thriving refugium. I also add pods
periodically and make sure he gets good share of frozen bloodworms every other day.