Yes fin nipping and Danio's, all danio's need a minimum of a 20 long tank if not bigger. They are very active swimmers and will pace your tank all day! So being a 2 gallon...yeah they wouldn't be very happy lol. There's really nothing else you can put it tanks that are smaller than 5 gallons. You could do a young Nerite snail but eventually they'd grow up all the same...so yeah.
Leopards: 1:4 Hawkeye, Luna, Astrael, Dorian, Cullen