Dosed Sulfur and now Alk is dropping like a rock

[Moe K]

Every ICP test I do shows low sulfur even when magnesium is in good levels. I am actually ~1500ppm magnesium (I know its high). Last test was Oceamo and sulfur was at 718 mg/L.

In an attempt to raise the levels I dosed Reef Factory Sulfur at there max recommended amount of 25ml per 100l of tank volume. I have 300 liters total so I dosed 75ml last night. According to their instructions that should have only raised sulfur by 10 mg/L in my tank. Today my dkh levels are dropping fast even though I have increased my alkalinity dosage. I have gone from 8dkh to 6.6dkh in about 24 hours and now getting concerned. The only thing different I did was dose sulfur.

The corals looked ok but I am worried that will not last too much longer if I can not fix the issue. I am going to just give a huge boost in alk dosing. Hoping it's nothing but a HUGE growth spurt as that would be great but alarm bells are going off.

Does sulfur affect alkalinity? Dosing my alk supplement I noticed a lot of precipitation.

 

[Randy Holmes-Farley]

I’ll make a few comments, but I do not have a perfect explanation and few folks have noted problems with off sulfate levels.

1. There’s very little useful information on what happens when the chloride to sulfate ratio differs significantly from natural levels.

2. That ratio is the only way that sulfate (sulfur) can deviate from natural levels at normal salinity, since it and chloride together make up the great majority of total negatively charged ions, which are largely fixed at fixed salinity.

2. Sulfate in general is an ion that most organisms use relatively little of, but some do, such as some seaweeds and microorganisms of various sorts. It is decomposed in anaerobic sediments, and that process depletes alk.

3. The biosynthesis of the amino acid cysteine from sulfate adds alk. Thus, increases in this process do not explain your results.

4. I see no reason to not add sulfate faster, if needed.

5. There’s no direct impact of sulfate addition on alk, but I do not know what exactly Reef Factory puts in their product. You might check its pH. It should be fairly neutral.

 

[Moe K]

The product just says sulfur reef minerals. There was a noticeable drop in ph when dosed. I won't be using this product anymore and will be purchasing magnesium sulfate to raise the levels slowly.

 

[Randy Holmes-Farley]

The product just says sulfur reef minerals. There was a noticeable drop in ph when dosed. I won't be using this product anymore and will be purchasing magnesium sulfate to raise the levels slowly.

Perhaps it is partly bisulfate, either by mistake or misguided intent. That form lowers alk and pH.