How do I make flying mobs stop staying still?

when i want a custom mob with the same type of a existent vanilla mob i usually extend its entity on:

public static class CustomEntity extends SquidEntity {
		public CustomEntity(FMLPlayMessages.SpawnEntity packet, World world) {
			this(entity, world);
		}

in this case i made a octoput that moves like a squid, i guess you can do the same for any entity, in theory