What your tank needs is bacteria, and you need to breed it before your new pets are added. A very easy way to do this is to buy one or two uncooked cocktail shrimp from the deli at the supermarket. Just throw them in the tank and let them rot. As they do, bacteria will grow as a result. Ammonia levels will rise in the tank over the period of a week or 10 days, then it will suddenly drop (you’ll observe this with your Ammonia test kit), and Nitrites will rise quickly over a period of another few days. is that a good idea?