I have just purchased a MH set from a store online. The set included the ballast for 2 175w bulbs the end caps seperate switches and mounting HW. it did notinclude bulbs. Total price 159.00. My question is qhat is the difference in the bulbs I buy at a reef store and the ones that I buy at home depot for 20.00 both are MH and 175w can anyone explian
