Deborah,
Lots of things in the tank may need the CaCO3, but probably not the shrimp. Their shells are made of chitin and contain little or no Ca, compared to snails, etc. I have found the trace iodide addition essential for several kinds of shrimp and even crawdads, I think.
A trick for avoiding the highly overpriced LFS reef iodide stuff is to feed plenty of kelp/spirulina flakes and/or use iodized salt for hatching bbs, etc.
Just avoid the premium brands that use silica gel for a free-flowing agent. Get the cheapest store brands that say "yellow prussiate of soda" on the box. It is sodium ferrocyanide and lots more soluble than the gill-scraping silicates. [They use the medieval name to avoid terrifying folks whose chemical knowledge comes from mandatory government schools.] The old-wives-tales cautions against using iodized salt are all based on the silicates, not the amount of iodide present.
Don't underfertilize to avoid traces of copper. It, too, is an essential trace element for sustaining life. Too little is as bad as too much, usually.
It is like oversoftening water killing plants and fish. Sodium is an essential blood electrolyte, but too much with too little of the others can become toxic. I added too much salt to raise the tds of my ultra-soft water in Modesto (tds 50ppm) and killed even the toughest Java Moss (which is often an estuarine plant!). My strain of Java Moss had previously done OK in nearly 50% sea water. [S.G. 1.015]
Moderation in all things seems to have a lot going for it.
Wright
01 760 872-3995
805 Valley West Circle
Bishop, CA 93514 USA
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