You just need to make sure it doesnt say "dolemite" anywhere on the bag. Some companies used such things as crushes oyster shell and cal it aragonite. Theyre both a form of calcium, its just that dolemite isnt the correct form for what is needed.There was a article in TFH that had a review, and they state most true aragonite is the same, but some add silicates, such as quartz, to take up more space and therefore increasing profits.