The most popular fancy guppy is the Moscow Blue Guppy. It's a beautiful, iridescent fish that has an amazing blue tint to its scales and fins that makes it stand out from other varieties of fancy guppies. This particular type of guppy was developed in Russia during the mid-20th century and is one of the most sought after types among aquarium hobbyists today. Not only are they very attractive but also quite hardy making them suitable for many different aquarium setups. They have broad caudal (tail) fins with various fin shapes including round, lyre, flag, spearhead and more. Colors vary greatly depending on which variety you choose with some having yellow or green bodies while others may be purple or red in color. They can reach up to two inches in length when fully grown so they require plenty of space as well as regular water changes to keep them healthy and happy!