anemones are inverts that house zooxanthellae like corals do. ( there are exceptions to both but these require even more attention )
bascially this algae (zooxanthellae) that grows in good lighting will be feeding your specimen. i would also suggest small food portions weekly-biweekly (with even more frequent if it doesnt contain zooxanthellae.)
in addition, nems will need proper alk, cal and mag levels and proper flow. basically they require a reef enviroment.
maybe we should start with what kind were you interested in?