Ok I started up a sw tank again and doing a fishless cycle with household ammonia, no surfactants or perfumes. I had nitrite spike after a few weeks. Then the nitrite dropped (although strange color vthe nitrite test was a turquoise color instead of the blue). The strange part is I have zero nitrates. None at all. As a matter of fact the tap water that I used to start the tank has 10 ppm nitrate. That is now gone out of the system in the tank. It has less nitrates than I started with. This has been cycling for 2 months. It's a 65 gallon long with a 500gph canister, 300gph hob filter and a hob refugium with a 4 inch sandbed. Protein skimmer and uv light are not hooked up yet as I did not want to hamper bacteria development. Ph 8.2 temp 76F. I have a tray of matrix in the filter. Could that be denitrifying already? Or the dsb in the refugium? I would expect there to be sone nitrate as I used a considerable amount. Any ideas would be greatly appreciated. Thanks in advance!!