Gary, or someone; Can you check in to this chemical issue?

[GaryP]

The question was whether there was a problem with high sulfates resulting from using Magnesium supplements which are mainly Magnesium Sulfate.

My reply was really a question. What data is there to support the claim that sulfates accumulate. Who has tested for it and if there is a problem, can anyone show me where high sulfates result in a negative impact.

Sulfates are exported by a couple of mechanisms.

1. Water changes

2. Conversion by bacteria to hydrogen sulfide that is a gas and off-gases like CO2 does through the skimmer and surface water gas exchange processes.

3. Deposition as Iron Sulfide, which is inert, in the DSB. This is the black stuff that you see in a DSB when you move a tank.

4. Sulfate is utilized by plants and bacteria for growth in much the same way that phosphates are. Since sulfate is rarely in short supply in water as is phosphate, it does not cause a bloom.

Processes 2 & 3 primarily occur in DSB the same way that denitrification does. This may be more of an issue for folks that are running BB tanks. The bacteria that do this are similar to those that process nitrate to nitrogen. They are called sulfate reducing bacteria (SRB) and are anaerobes or facultatives. They were first discovered in ocean sediments. Desulfovibrio is the most common of these bacteria.

This discussion is similar to the arguments that went on a few years ago about the negative impact of chloride buildup from the use of two part additives such as ESV. The difference is that sulfates aren't inert like chlorides are. They are used by plants and bacteria and cycled. Just as we talk about nitrogen and phosphate cycles, there is such a thing as a sufur cycle too.

OK, is that Spam or just TMI?

[TexasTodd]

Ahh, good recap G-man.

Scuba, you just worry about having a baby!

Todd

[GaryP]

Why do I even bother trying to explain the beauty, mystery and elegance of chemistry and microbiology to an engineer? My guess is that he will be searching online for an automated sulfate monitor powered by a super computer and designed by some guy named Wolfgang by the end of the day.

J/K Steveo....

[GaryP]

Just another point. Here are the alternatives:

1. Magnesium Chloride - good product, but it will only add to the chloride buildup issue. Chlorides don't cycle like sulfate.

2. Magnesium Sulfate - See above.

3. Starve your corals for mag. Another issue is that magnesium plays an important role in helping to maintain the calcium/alkalinity balance in the aquarium. Not enough mag and you end up with a calcium carbonate precipitation problem. That means crashing levels of both calcium and alkalinity, burned up pumps, and a nice white tank that will look more like Fargo, ND in January then a reef in Tahiti.

[gjuarez]

Great info, Gary. I have a bb tank and I may not have the anaerobes and faculatatives to process the sulfates. Is this stuff taken out by the skimmer? What can be the negative impact of elevated levels of sulfates in a reeftank? Am I just worrying too much?

[GaryP]

Jerry,

That was my whole point. I have never seen anyone report a negative impact from high sulfates. A skimmer won't take it out. Its completely water soluble. Skimmers only remove stuff that are hydrophobic or bound to hydrophobic molecules. If we need stuff to keep us up at night worrying about our tanks, I can think of better things. As for your lack of bacteria, that's part of the problem that goes along with BB. The bugs in the LR will so some of the things that a DSB does, but maybe not as well or as efficiently. You can still manage it, like everything, with more and bigger water changes.

I guess that's my whole problem with BB. I'm rarely in favor of a solution that means working harder and not smarter. Sure there are disadvantages to DSB, just as there are with BB. I guess it just comes down to what works for you. For me, putting more time into my tank is not a viable solution. As much as I hate to admit the comparison, I'm with Dr. Ron on this one.

[brewercm]

My bad, that post was supposed to be after the few you had about the professor waiting. Some way it ended up about four posts later than I posted it.