I would agree with Jen that they are the exception. Mine started eating frozen food beginning with RODS, then PE Mysis, onto pretty much anything I throw in the tank (pellets, flakes, cyclopeez, etc).
One thing to note though (in my opinion/experience), keeping a mandarin healthy requires CONSTANT food. If you have no pods, you need to be turning your pumps off and feeding heavily several times per day or they can deterioriate. Mandarins aren't as aggressive as other fish in the tank and if the pumps are on and food is blown around they will rarely get enough food to sustain a healthy size.
I had a massive pod population wiped out about 6 months ago when I went on my quest to rid my tank of red furry algae (which I was mostly successful with). The mandarin has lost probably 30% of its size, to the point of being dangerously low. I am at the point now of rebuilding the pod population and hopefully getting him back to a good size. He still eats anything I put in the tank 2x per day, but it just hasn't been enough for him and I've been cautious in "over-feeding" because of my algae fight.
I guess ultimately what I'm saying is that yes, some will eat prepraed foods, but there are some caveats to keeping one alive and healthy on a completely "non-pod" diet.