Cheaper isn't always better, you get what you pay for. Prime is good but it a chemical product unlike ML which is all natural and overall better for the fish. All ML products work great together and can be combined to do even greater things and you never have to worry about over dosing. You can cycle a tank in 24 hours with ML, beat that. ML is about quality and the peace of mind when using it and the effect on the fish is unmatched. I don't work for them but I should be getting paid for this ha ha.