I came from about the same position you did. I water changed weekly for decades!! For the most part you can make your own and SAVE a TON of money. You can dose Alk and Calcium with Mrs Wages pickling powder (calcium hydroxide), or just Alk with baking soda (sodium bicarbonate), or just Calcium with Calcium chloride from the local pool supply, and Magnesium with Epsom Salt (magnesium sulfate). The stuff I buy is Strontium (Kent) and Kent Marine Iron & Manganese.