no, definately not necessary to do a daily water change unless you are keeping a well-stocked discus tank or something.
is it a 55 gallon tank? how many fish and what size?
for a typical moderately-stocked cichlid tank i would stick with a 30% water change every 7-10 days.
if you dont mind doing more, by all means do more. it wont hurt anything.
generally, most people like to keep nitrates below 20ppm in their tanks......<10ppm is even better, and usually what i keep my tanks at.
HTH