So I'm a little confused here, I've had a 100g/400L Reef tank set up and established for 2 years. Never had any problems except for 1 round of white spot after about 11month which unfortunately caused 14 fish to die leaving only 4. After almost 13 months of no issues now my nitrates have spiked I think.... I test with API I get 30,i test with sailfert I get 80, red Sea its so high even when diluted I can't tell, tetra I get 50 and the lfs five in total all test different as well. My fish are fine, my inverts are fine (abalone snails are breeding like mad) and my soft corals are thriving. I have a refugium, carbon and dose no pox, fluidised Reactor, uv and even a hydro stream 2, I've completely cleaned and relaid my sump and upgraded my protein skimmer, changed my ro filters and tested it as 0 and done huge water changes but still all tests show different even the lfs is stumped. Surely having 100 or close would cause fish loss or at the very least inverts and corals. Obviously it's not affecting my tank or its inhabitants thankfully but seriously I'm stumped, any ideas?