I compared them label to label. I found it quite interesting. The XL had like 5% less protein. No mention on the Thera jar about what it is that makes it anti parasitic though thats been assumed to be garlic. I can tell you that the Thera does indeed sink. About 50% sink. I've been feeding my cichlids Thera for a while and cant complain but NLS is pretty good overall IMO. I found a guy on Craigslist with pretty decent prices and he delivers. Let me know on your guy's prices.