ouch nitrate is really high. im no marine biologist but i think you are do for a partial water change janey.
already got the green algae in 4 weeks wow. i got mine in about 3 months. and then i got the red. hehe i hate that stuff but thank got its on the sides. not the front.
I'd just do a 100% water change...then wait a bit and see if the nitrate rises...it may not and you're all good...if it does rise then you need to re-think your maint/set-up.
If the test is indeed 100, you need to do a major water change before proceeding. Sorry to slow you down at this point, but you need to make sure the tank isn't producing that normally or everything you put in there will die.
There is a normal nitrate level after a cycle, I don't think 100 is within the realm of normal unless the rock was sitting on a loading dock without water for a week or so.