High nitrates , 0 phosphate help!

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Hey guys , so I am stumped been in this hobby for 10 years and never had this issue..

So this is a new tank been running for about 11 months . No corals , 5 fish , and my nitrates have been hovering around 60 ppm
For the last 6 months ... I been doing weekly 30% water changes for the past 2 months (was doing twice a month prior) but no change. Using a seachem test kit my phosphate is 0 clear as day . I cant get my nitrates to drop with feeding once a day.i have never had so much problems with nitrate in my previous set ups and I am out of ideas.. and fish are happy

Specs:
180g tank with 55g sump
Over 200lbs of live rock
Vertex 180 skimmer
Less than half inch sand bed

Thank you kindly

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