A tiny net can be purchased from Harry in Catherby for 10 gold. It is used to get a pet fish. The player has to have a fishbowl filled with water and seaweed (can be caught in a big net) in the inventory to buy this net and fish food for a pet fish. Once the player has this kind of fishbowl in your inventory, ask about getting a fish and buying a tiny net becomes an option. These nets can only be used if your fishing level is above 10.