No celestial pearl danios should be kept in a 5-gallon tank. Despite their small size, these fish need a minimum tank size of 10 gallons.
This is because these fish need a heavily planted environment. While a similarly sized fish only needs one gallon of swimming space, each celestial pearl danio requires two gallons to compensate for the area dedicated to plants.
Moreover, celestial pearl danios prefer living in groups, so you should keep five to six of them together.
Because each fish requires approximately two gallons of swimming space, it’s impossible for them to fit into a small 5-gallon tank.