High Sulfur

[DBryan]

icp test shows sulfur 1165 mg/l . what would be the cause and how harmful to corals. R.O water 0 sulfur.

 

[Randy Holmes-Farley Verified Community Expert]

Sulfate is the third most abundant ion in seawater by mass (after sodium and chloride, before magnesium). It would come from your salt mix, or from a lot of sulfate based additives, such as Epsom salt for magnesium, or just high salinity.

FWIW, we really have no data on how important the sulfate to chloride ratio is in seawater, but if salinity is normal, the only way for sulfate to be high is for chloride to be low.