Depends on the size of the nano tank you are getting. You can get either a hang on filter or a cannistor filter.
At a very minimum, you need a filter compartment big enough for you to put in a wool filter, bio rings, Pura Nitratelock and Pura Complete or Phoslock. You will also need super bacteria to dose your bio rings so that bacteria will grow on them and it will help to reduce your nitrates & phosphates in your tank. Just take note that ceramic rings are not recommended as they are not porous.
You will also need a protein skimmer and a chiller to keep your tank temp to between 25 & 27 degC.

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