According to my Salifert test kit, my tank's Mg is sitting at >1500- their chart only goes up to 1500, and I emptied the syringe before I got a color change. I tested my mixed saltwater and it was 1440. I use Instant Ocean Reef Crystals, and did a 15g water change yesterday on my 120g tank with 40b sump (approximate total volume around 150g). I repeated the test to be sure, but got the same result. Why would my tank's Mg be elevated out of reference range when the salt mix wasn't testing that high? If there was something wrong with the test reagents, wouldn't both the tank water and the barrel water test out of range? Assuming the result is correct, will a Mg level that high harm my corals? I don't have many and they're not fancy- zoas, trumpet, duncan, monti cap, hammer, digi- but I don't want to burn them. Thoughts? Thanks for your input!