don't believe the hype about ORA mandarins, or mandy's being "trained" on frozen.
i'm with snorvich on this one, every mandy i've ever met will eat frozen if they can get it, however due to their physiology and inability to effectively compete, you still need the right sized tank and the pods to ensure long term success.
these fish are grazers, all day long, to the exclusion of almost everything else. one, two, three, or even four feedings a day aren't really practical or sufficient to make them sustainable.
you will hear stories of success in smaller tanks, but those are the exception, certainly not the rule, and i would be cautious of anyone declaring success prior to the one year mark.
if you are rock heavy, have a good substrate, and established tank, no direct pod competitors, and a large, productive fuge, then you're right on the cusp of what is acceptable to sustain a small mandy. obviously bigger is better, but given those criteria, and at least a tank established for about one year, you could potentially pull it off.
take away any of those points however, and i wouldn't try it.
in regards to culturing the pods, this can be finicky. cultures usually take between 4 - 8 weeks to start producing in numbers large enough to harvest. they are also temperamental and prone to crashing without warning. so i treat external cultures as an insurance policy, not a given.
in tanks that are on the lower, and vigorously debated, end of "acceptable" it's always good to take a hard look at how much risk you're willing to take. larger tanks give you larger margins of error with obligate feeders such as these. you also need to take stock of just how much supplementation you're willing to do. PaulB has constructed some very clever, and extremely useful, feeders for helping to supplement fish that prefer small, living prey like mandy's and pipe fish.
so let's talk it out:
what else do you keep, and what are you planning to keep?
how much rock is in your display and sump?
you do have a sump, right?
how big is your refugium?
what kind of substrate do you have?
know that having one of these fish will dictate future stocking options to a large extent, especially in a smaller tank such as yours. all wrasse would pretty much be out of the picture. pipefish would also be a no go. pretty much any other competitor for pods would be off the list, and since a 50 gallon is too small for tangs/angels/etc... you may find that unacceptably limits your potential stock options.