Delta Tail Guppy Male, totally ignoring the colours if you look at its name which would indicate a triangular tail, well to be honest if one said no this is a halfmoon blue guppy i would agree as well. Open for debate the names of guppies are, but whats more important is how do they look overal, you decide. This type of guppy fish is often considered to be among the most beautiful of all guppies. They have a long, slim body with a sharply pointed tail. They are a popular choice for aquariums because of their unique coloration and their ability to thrive in a variety of environments. In addition, they are very hardy fish and can withstand the harsh conditions of an aquarium.