I posted this question in the intro section also

Hello we are John and Michelle,
We just started our first tank (well I had a marine tank many many years ago with a under gravel filter) LOL its been a while. Any way we got it from our friend next door and are setting it up as a reef tank.
We moved most of his water with the tank (56 gal bow front) he had a fish only tank. with 2 Ehiem canisters. Now I have a huge Nitrate problem and I have lost Coral and several fish. It’s been about a month now and I have done LARGE water changes, added nitrate reducer and bought a hang on protein skimmer. I'm still at 20-40 ppm Nitrate any suggestions?

The source of Nitrates in an aquarium is usually spoiled protien, either from overfeeding, dead fish or fish waste. I'm sure you know that Corals are very sensitive to Nitrate. Because the Ocean is so biologically active, Nitrates are very rare in Coral Reefs. Another problem you can get with Nitrates is Algae. Make sure you have good filtration and chage your filter pads frequently. Old, dirty filter pads are a constant source of nitrates. Make sure you have a good protien skimmer, they remove stuff that eventually becomes Nitrates. Also, make sure your source water doesn't contain Nitrates. There are so many sources of Nitrates in water systems these days it could easily happen.