I just cycled my first reef tank (Red Sea 900 L including sump and refugium) and the nitrate are around 100 ppm (new Salifert kit, ran 3x and followed directions making sure to look down through the vial from the top - the solution is very pink ), which seem ridiculously high. I used RO/DI water (from LFS, but have now purchased my own RO/DI unit) and have dry rock (Marco) and dry sand (CaribSea) and haven't added any food and all rocks are new. I used Dr. Tim's method for the first time (dosed a total of 120 mL of 40 mg/mL ammonia in 2 portions) and seeded with bacteria (16 oz of Dr. Tim's). Based on the added ammonia, I would expect nitrate should be ~20 ppm. I saw Randy post that nitrites can interfere with nitrate tests, so made sure to test and have 0 nitrite. Any suggestions on potential sources of nitrate would be appreciated or is it likely that the Salifert test is over-estimating the nitrate concentration? The tank is about 4 weeks old now and I keep the lights off, so fortunately, the water remains clear (no algae growing yet). I would love to start my refugium, but Chaeto is not available.