There's not a single chemical at the petstores that you need to put in your tank. You're almost better off just emptying your wallet directly into the tank. Same waste of money and at least you know what you're putting in

Now planted tanks or reef tanks requiring bottled food / fertilizers are a different story but sludge, ammonia, PH, water conditioners, take your pick of miracle in a bottle is not ever needed. Remember our friends live in these tanks. The more chemicals you can keep out of the water, the better.