I see.
It’s almost impossible for magnesium to be anywhere near that value.
I’ll explain why:
1) Instant ocean is wildly proven through decades and ICP testing: the magnesium is around 1280-1300 ppm, which is near natural seawater. It will be highly unlikely to receive such a faulty batch.
2) All For Reef contains magnesium. It won’t account for 100% consumption, but it does supply enough to prevent such drastic readings.
3) Most importantly, it’s mathematically and chemically unfeasible for magnesium to drop that low through consumption.
Magnesium depletes very slowly in exact ratios found in calcium carbonate, either through abiotic or biotic precipitation
2.8 dKH alkalinity, 18-20 ppm calcium, and 1-2 ppm magnesium
Coralline algae has a higher affinity for magnesium, since they are made from magnesium calcite instead of aragonite, so we’ll use the upper end to show that even in extreme cases, this value is highly unlikely.
To drop 50 ppm magnesium, you’d also need to deplete 70 dKH of alkalinity. This is worst case scenario, assuming you predominantly have coralline algae and only used sodium-based alkalinity additives.
4) Couple that with the fact magnesium kits are notorious for displaying dangerously false lows, I wouldn’t put any validity in the accuracy of home kits.
In fact, I would never even bother measuring magnesium at home. If you genuinely wanted to know, ICP would be the way, but I doubt it will lie anywhere near that reported level.
