These are Gaint danios (Devario aequipinnatus), very common around southern part of India, when kept in numbers they do look great (especially males get more blue they grow upto 4" in the wild , but might grow a bit more with good care and feed))
On a typical fish catching trips we make can catch upto a few hundreds in the span of few beers!
Some LFS guys also use these as feeder fish which can give the aros some exercise as well. But i have noticed that eventually others monsters get tired of chasing them around and live happily ever after.
PS: they breed like nuts (fry food maybe?)
Projectile