unless you have upward of 100 # live rock that has been established for over a year in a healthy environment, you will kill the mandarin.
and i am sure htat there are plenty of people tha tare dying to chime in about their mandarin that survived for years in their fish only system eating brine scuz, and pellets, but these aeople are a great exception to a concrete rule that is readily ignored and the expence of the demise of the mandarin.
they are tempting, indeed, with the best color in teh ocean and a miniscule price tag to boot, but they do require a very specific diet that cannot be replicated without folowint eh reccoemndations listed above.
snowflake eels eat shrimps and small fish in the wild so i would not rish the shrimp for the addition of an eel.
i am certainly not the tang police, but i have yet to see a tang truely happy in less that 6ft of swim space.
when i recently set up my 180, i saw my purple tang gor from what i thought was a happy fish (in a 75) to a fish displaying brighter color, more natural swim behavior, and more resistance to disease. they really do need the space the tang police say. they have made a believer out of me.