The "waiting 24 hours" advice does not do anything to cycle the tank. Firstly, beneficial bacteria cannot establish itself that quickly. Second, there would be no food source for the BB to eat (AKA fish food) while it is cycling. Do you have a tank that has been established for at least 3 months? If so, then take the filter cartridge out of the filter of your established tank and simply squeeze the "dirt" off/swirl it around in the tank. Yes, it will look messy, but the establishing filter will clean it up. Plus, you have just instantly cycled your tank! But, be sure to add fish slowly, and, you should add the hardiest fish YOU WANT first. Don't just add a zebra danio/ guppy just because you want it to cycle your tank; you'll just be left with unwanted fish in the end. Just buy the hardiest fish in your stocking list to cycle the tank. It might not be as hardy as a zebra danio, but a lot of fish that are "fragile", like German Blue Ram cichlids and Otocinclus are actually a lot more tolerant of water conditions than you think. You should still add the hardiest fish just to be sure, though.