I started cycling my sw aquarium with live rock 3 weeks ago. My ammonia and nitrite readings went up and came down to 0mgl. I did a PWC removing 5 gal from my 30 gal aquarium. My nitrates are currently at 100mgl which I believe is high. What should I do??? My specific gravity is at 1.022, pH is 7.8, and the temperature is at 78F.