Hi Puneet.
Aquarium fishes (Ornamental fishes) can broadly be classified into two varieties. Live bearers-which give birth directly & egg layers-which lay eggs. These eggs hatch from within few hours to a few days. Each variety of ornamental fish breed in different climatic conditions like temperature, pH of water, hardness, salinity etc.
Small fishes give birth to less number of off-springs & big fishes give birth to plenty of small fishes-called fry.
Any living creature will breed but the art is to take care of the young ones by giving them proper feed according to their size & reducing the mortality (death rate) of the young ones by proper hygiene inside the tank.
Different types of worms are cultured by ornamental fish breeders before they start breeding the fishes. These worms are then fed to the young fry. Artificial feed is also prepared by the breeders for later stages when the fry become bigger in size to enhance the colour of the fishes, their shape & appearance before the fishes are sold in the market.
Please contact the local fisheries department who will guide you. Each district in the country has an Assistant Director of Fisheries & they are quite helpful. You will however have to approach local ornamental breeders for more details.
Good luck.
S. Kapoor