I use the 1 unseasoned, raw jumbo shrimp per 30 gallon fishless cycle....51 cents is a lot cheaper than stuff in a bottle or risking the life of a poor fish. You could also use fish food or as stated pure ammonia.....
Unless you are a LFS and want a double sale, for the cash, they generallt tell you to use fish....drop the fish in, maybe it dies, you have to by another fish and they make money...or better yet, they tell you use damsels, they make it through the cycle and you add more fish to find out the damsels are terrorizing/killing/stressing the new fish and then you spend a half a day trying to get the damsels out of the tank....