Rainbowfishes are gaining popularity because of their colors and activities. You can ty some and tey also go best in school. There are a lot of different species that can be found in different stores. Personally, I like the Dwarf Rainbow, Melanotaenia praecox. Corydoras are good scavengers. There are a lot different species to choose from, Bronze (the common and cheapest), Panda, Sterbae, Pepperred, etc.