Swordtail (lat. Xiphophorus hellerii) is one of the most famous and spread tank fishes. In general this fish is quite peaceful and it can inhabit in a common tank. Though each fish may have its own temper, which can be both timid and shy or aggressive and blusterous. This is especially true for males. They can be aggressive towards each other.
Guppy (lat. Poecilia reticulata) is a renowned tank fish. Even people who are not into aquarium husbandry know about this fish, not to mention aquarists. Each of them has surely had a guppy fish in a tank even just once.
Some aquarists started their hobby from buying a couple of fish and even now they have some splendid selective breeding species. To answer all the questions about this fish we’d have to write a book, but we’ll try to discuss the most common ones here, in this article.