This is my first large tank, and i plan to have 8-12 tetras, 2-3 corydoras, and a betta. According to what i have read, these fish should get along in 20 gallons depending on how the betta acts. When and how much should I feed them? I know that they all can eat flake food, but how can i make sure the corys at the bottom get some? Please tell me if theres anything else i am overlooking. Thanks!