We have a Mandarin & I have purchased Aquapods in the past. I found them for $20 per bottle (think small, travel bottle size). Our tank is 100gal with 130lb liverock, and I've purchased 6 bottles in the 8 months we've had our Mandarin. He is huge & healthy, but we are a MAJOR exception to the Mandarin rule...our guy will happily eat Formula One & Two pellets & any sort of live or frozen brine shrimp. So I never worry about having enough pods.
I have read that if you want a Mandarin, you really need a refugium box to keep your pod supply high enough, or your Mandarin will slowly starve. I could be wrong, so please, anyone, correct me if I am!