Welocme to the site! In your signature, you say you have a clown loach? only 1 zebra danio? 1 serpae tetra? you need more danios and serpaes-they're schooling fish. in fact, all of the fish in your tank are schoolling, so you need at least 3 of each. but 3 clown loaches in a 20 gallon? just 1 is too big for that tank!