I've not tested high sulfate effects on marine life.
I'm not sure if anyone knows if higher than normal sulfates are in fact toxic in our tanks, but an imbalance in chemicals is never a good thing.
Some believe that high sulfates can cause changes in organic consumption, this could imbalance the nitrogen load of the tank. In other words, one thing has affected another, thereby causing a problem.
"jbarone" doesn't say how he boosted Magnesium, but in Epsom salts sulfates are roughly 4:1 to magnesium by weight, I believe. Other mixes are different, of course.
Assuming he did use Epsom salts, then this means that if he's approximately 100ppm too high in magnesium (currently at 1525ppm, 1425ppm being more ideal), that he's added greater than 400ppm sulfate. (..and this only accounts for the amount he's over, not the total sulfate addition)
One assumes that when he added the suppliment, that he was lower than 1425ppm magnesium to begin with (otherwise why would he add magnesium?), so the sulfate addition is likely much higher.
We also do not know what his starting magnesium was, and if this was done all at once or in steps, or if any water changes have been conducted over the course of magnesium additions.
Given the information at hand, we only know that his magnesium is higher than normal.
A water change, in this situation, is simply a cautious approach.
<a href=showthread.php?s=&postid=9932893#post9932893 target=_blank>Originally posted</a> by marsh
http://reefkeeping.com/issues/2006-02/rhf/index.php#23
http://reefkeeping.com/issues/2006-07/rhf/index.php
BONDQ
I did not consider the source of the Mg. Certainly if you dose Mg as MgSO4 (Epsom salts) only, and not a more balanced addition such as Randy's part 3A (5 parts MgCl2 3 parts MgSO4), SO4 will rise.
I am more intrigued by "sulfate toxicity". What are it's effects and manifestations?