Here are some things that are known to reduce nitrate in no particular order. Copied from a post I made to another thread. Not everything may apply to your tank. 1. Change your substrate from crushed coral to sand 2. Add more rock to your tank. (live or dry) 3. Get rid of the wet-dry filter and the bioballs. 4. Convert the wet-dry to a refugium with a deep sand bed. 5. Add chaeto algae in your refugium for nitrate export. Light the chaeto on a reverse ligut cycle. 6. Increase flow in the tank. 7. Eliminate all mechanical filters. My only mechanical filter is my chaeto. Any trapped material is consumed by pods and bristle worms. 8. Eliminate any bio-wheels in your system. They are great nitrate factories. 9. Reduce feeding. Feed every other day and reduce the amount.