I really am interested in this topic. As I have stated I am considering the use of dolomite and because I know the composition and particle size of Mighty White
composition through somebody else’s previous post I will be waiting till spring for Crappy Tire to import it. (I will not take chances with the others.) It is sealed in a plastic bag and I would not consider it to be a major problem. I have worked in warehouses where they handle both sealed food and chemical products (though not as nasty as pesticides) and if they consider that we are safe from it then I'm not going to fret over the fish.
Right now I am researching it and came across a post by Randy Holmes-Farley in another forum where he says "After all, where would the magnesium go? It's not being precipitated inside the plant (I presume), so it is likely being actively pumped out of the plant by another protein to maintain normal internal magnesium levels. A 100 gallon tank contains 492 grams of magnesium. To significantly deplete that, the plant would need a huge sink for all that magnesium."
To me this suggests that first, magnesium is not depleted very rapidly " Fortunately for reefkeepers, it is present in abundance in seawater and is depleted only slowly." (From the above link.)
And secondly it seems to me that 492 grams in a 100 Gal tank is a lot. (love how everybody combines metric and imperial measurements these days.) It would seem as though there should be some room for a bit more without affecting the organisms negatively. (I could be wrong as I am not a chemist nor a biologist.) It just seems that with regular water changes there is room for some of it to dissolve. It seems doubtful that a DSB would even dissolve 10 grams of magnesium each week because it would not be very long before you would have no sand bed.
In the same reply Randy suggests using a Hatch kit to test both the magnesium levels and calcium levels and it would be interesting to see the results in a tank with a dolomite bed.
As to the question of how polluted the dolomite may be, I have given it more thought. First, the pollution of the operator using the ground as a toilet should not be a huge problem as the nitrates etc would get taken away in the tank the same as fish waste. If I recall correctly there was even some suggestion that clams even need the nitrates and yes, you could use your tank as a toilet to provide it. (Bad and rotten as that may sound, it would keep others from reaching in your tank [img]images/smiles/icon_biggrin.gif[/img] .)
The grease would be minimal and as I said there would be very little oil in the finished product when you consider that they would be using a loader with a 5 cubic yard bucket and even if there were a small leak it would provide less pollution to a fifty pound bag of dolomite than I do when I reach in the tank to clean the glass after working on cars. (Yes, I do wash, but there must be some residue.) If you were concerned with the hydraulic fluid you could skim the top of a bucket you poured it into first.
I do not care what they say, there would be a minimal amount of metal in the aragonite. They are not digging it out of the ground with a plastic machine and sand is VERY abrasive to the bucket of any machine. Also they screen the finished product so they can sell sugar fine etc... and they would run it over the same metal screens as the company producing dolomite would. The only difference that I can see is the metal off the crusher at the dolomite mine and even then it is a very small amount when you consider how much product is produced to wear a set of hammers down.
No matter what machine the company pulls the aragonite off the ground with I would bet it is well greased as pins and overhauls are expensive. I am not sure that they have not taken some steps to ensure that no grease gets into the product, but I have never seen a loader or excavator that would not pollute the end product with just a little.
One last chemistry related thread and comment on the dolomite. Here is a quote from aquarium frontiers where the author is talking about limestone versus crushed coral in a reactor. "The limestone was significantly lower than the crushed coral in a wide range of trace elements, including aluminum, boron, chromium, cobalt, copper, iron, phosphorus, silicon, sulfur, titanium and vanadium. Of particular concern to me were the lower concentrations of iron and phosphorus in the limestone compared to the crushed coral I’d been using." And "Comparing the limestone to the Super Calc Gold analysis performed by Bingman...shows the limestone significantly lower in aluminum, copper, iron, manganese, lead, mercury, nickel, silicon and zinc."
Anyhow, the link to the whole article above is right
here.
I hope that provides some food for thought. I am not saying that dolomite should be used and I am having some second thoughts about it myself. However, from the info I was able to dig up it does not seem like it would cause a system crash and I found it interesting that it was lower in the heavy metals.
-Danny
On a side note not related to reefs but related to my sanity I keep having a pop-up widow appearing to me that comes up as a rotate…html. If anyone can tell me how to rid myself of this annoyance I would really appreciate it if you could e-mail me or send a PM. Thanks.
[ 22 January 2002: Message edited by: dan150 ]</p>