if your fuge is productive and you have a heavy amount of rock you shouldn't need to dose them that often. the key is waiting a while for the population to establish itself, 6 - 12 months is usually my recommendation, since their populations tend to go through boom and bust cycles.
i recently migrated my 75 gallon to a 150 gallon. i'm rock heavy, i was running about 125 pounds in my 75, and added quite a bit of additional for my new tank. i moved over all the old rock, and large doses of the sand over a period of two months.
i was also dosing phyto and ghost feeding to help give them something to eat.
then i seeded with a half gallon of pods from Algae Barn, just to help boostrap the populations.
the rock from my previous tank was about 4 years old.
i have more or less the same condition with my girlfriend. she doesn't complain about the tank as long as her mandarin is happy and healthy.
likely you would be best to add the mandys at the same time, and like i said a male/female pair is your best bet for success.
i'm not sure how familiar you are with the fish outside of their feeding requirements, but picking out good specimens is as crucial as the tank configuration in helping to ensure success.