I have two mushrooms, a little green star polyps, a toad stool and a open brain coral and a new torch. My ammonia and nitrites are all 0. My nitrates were at 5. Before I left for 8 days now its 40 ppm. I have 7 fish. A eshopp skimmer rated for 150 gallons my sumps rated for 200 gallons and maybe 60 to 70 lbs of live rock it's a 90 gallon tank. My corals have been growing my toad stool was my ugliest coral and now its one of the most beautiful the mushrooms are doubling in size. I don't get it. I use API I did the test twice. Can anyone explain where are some soures of nitrates can come from? I make sure my filter socks are clean. Any ideas?