Instant ocean help

[Randy Holmes-Farley Verified Community Expert]

My understanding, from researching into the issue & multiple sources. Like this guy (Tidal Gardens, also Fish of Hex, Coral12g)
Even on the bottle of Seachem Reef Complete.

Also I remember reading from an article that you need Magnesium to help things along. However my levels were never low, and in par with the fresh batch of Instant Ocean.

dang good thing I followed the great advice - don't put anything in the tank you can't test against. That and don't be afraid to do WCs.
It just freaked me out that Instant Ocean has such high numbers, and kept losing fish even when phosphates were below 0.03.

I think from now on I'll make new water at s.g. 1.025 on the nose from now on. Since I don't have an ATO yet, I add manually ever other day in the overflow box pure RODI as needed.
When I start the next batch of SW I'll test that first.

Perhaps using the 5g bucket, versus the box with 4 bags, the mix isn't what it should be. Perhaps some of the mix settles differently during transportation, like the Brazil Nut effect.
This bucket is halfway used up, then it's the box that makes 200g / 4 bags. Going to mix these up good for good measure.

I think it is not so clear as you or they are making it out. The effect is more often the opposite of what you are suggesting, and raising magnesium will not cause a sudden depletion in alkalinity.

One of the main effects of making sure magnesium is adequate, or even elevated, is to reduce abiotic precipitation of calcium carbonate, which is a portion of the demand for calcium and alkalinity in any reef tank. It gets on pumps, heaters, and sand and rock surfaces. In that function, raising magnesium will reduce the demand for calcium and alkalinity.

It is possible that elevating magnesium may boost coralline algae growth, and if that happens, you will see increased demand for alkalinity and calcium. Unless it is greatly depleted, I have never heard anyone make the case that coral growth rates are dependent on magnesium levels.

I discuss these effects in detail in these articles:

A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2006-06/rhf/index.php

Aquarium Chemistry: Magnesium In Reef Aquaria ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/issues/oct2003/chem.htm