Mandrians are difficult to care for. Your tank would need to be established for about a year before even putting a Mandrian into a tank with enough rock and sand to keep a population of Pods. Even with a healthy population of pods at first, one mandrian can wipe them out. That is why a lot of people maintain pods in a refugium under their tanks. That way they have a place to breed and grow without being eating right away so you can always have a stock of pods for your Mandrian.
Right now you can keep buying them to feed your guy, but that can get expensive. You can do a HOB refugium to help maintain a population. IF you want to keep this guy, I would buy that for now (unless you have a sump with a refugium in it already), and keep buying pods once a week.
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Buying Pods is going to get expensive, so I would suggest you get the HOB refugium, and some small chunks of live rock to fit into it to give your pods a place to grow and breed. I am unsure if it would need a light, but you will need to keep it warm, which I am sure your tank heater will do already.
I would get the refuigem and add a bottle of pods each week for about a month or so. Remember, your guy is eating them already, so you will need to keep supplying until you see a lot in your refuigem. That is why a lot of people do it before putting a Mandrain in. If your handy, you can build your own refuigem, their really not that hard and it would save you $100 or so.