I dont know anything about this fish, but I just came across the following info that suggests its possibly best suited to brackish water. Something you may want to consider.
Common name: Crazy fish
Scientific name: Butis butis
Origin: Found across the Indo-Pacific from Fiji to the coast of East Africa.
Habitat: Usually found in weedy rivers, swamps and mangroves. Found in marine, brackish and freshwater environments.
Water: These were being kept in a centralised system containing freshwater with salt added to a rate of around 3g/l. They should adapt to freshwater if done slowly.
Diet: A micropredator which eats shrimps, prawns and fish. The one shown here accepts flakes.
Size: Up to about 15cm/6”.
Aquarium: Needs a tank of about 90cm/36” or more, containing some shelter from plants or bogwood. Do not keep Butis with fish small enough to eat.
Steve