Calcium carbonate is a inorganic chemical produced from the a reaction between the metal calcium and carbon dioxide. The most comon form is limestone. Oyster's also create calcium carbonate to make their shells. There is no particular "potency" factor and the expiration date is meaningless (unless you can get a lot of people to replace their 2/3 full bottles with "fresh" bottles) One reason I can think of for the expiration date may be that the companies involved are ISO-certified. ISO-certified products must carry an expiration date from the manufacturer. I can't answer your question about the electrolyte, except to caution you about upsetting the electrolyte balance of your reptile. Under normal circumstances a reptiles electrolytes are balanced by a normal diet,adequate hydration and normal climate control. This balance can be upset by vomiting, diarrhea and dehydration. In these cases, from what you mentioned, you should dilute according to the label and rehydrate your reptile with the solution. Potassium levels are particularly critical. Too little can cause heart arrythmia and death while too high is also fatal. Sounds like you have all of your bases covered and are taking superb care of your herp. I have found with my three that gut-loading their food and keeping their UVB lighting replaced has yielded great results (at least so far-LOL) I do give my females liquid calcium during the breeding season to help with egg production/formation. Good luck with yours!
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dianedfisher@yahoo.com

My 3 CWD-Avanyu, Tripod and Drago