nitrates are driving me up the wall

[68shelby]

I literally have no algae, all the fish are healthy, the clowns lay eggs every 2 weeks unless I **** them off with a good tank cleaning seems to disrupt there cycle. Corals are all growing especially the mushrooms. No my biggest issue is the water changes. I use to do 5-10% a week and my nitrates just started to come on. now I am at 25-30% almost weekly and am getting tired of getting nowhere with it. Its expensive. I use ocean pro salt and bottled water. Where do I draw the line do I go back to 10g a week and watch how high the nitrates climb? or do I keep spending $250.00 a month on water changes. Thanks for the input I will definitely consider several things mentioned