Goldfish (Pond Size) Goldfish are a NORTHERN FRESH WATER FISH which can also survive in tropical areas just as well as it can extremely cold environments. The goldfish (Carassius auratus auratus) was one of the earliest fish to be domesticated, and is still one of the most commonly kept aquarium fish. A relatively small member of the carp family (which also includes the koi carp and the crucian carp), the goldfish is a domesticated version of a dark-gray/olive/brown carp native to east Asia (first domesticated in China) that was introduced to Europe in the late 17th century. The mutation that gave rise to the goldfish is also known from other cyprinid species, such as common carp and tench. Selective breeding over centuries has produced several color variations, some of them far removed from the "golden" color of the originally domesticated fish. There are also different body shapes, fin and eye configurations. Some extreme versions of the goldfish do need to be kept in an aquarium—they are much less hardy than varieties closer to the "wild" original. However, some variations are hardier, such as the Shubunkin. The main varieties are Common Goldfish, Black Moor, Bubble Eye, Celestial Eye Goldfish, Comet-Tailed Goldfish, Fantail, Lionhead, Oranda, Pearlscale, Pompoms, Ryukin, Shubunkins, Demekin, Ranchu, Panda Moor & Veiltail. Ours are somewhere between Common and Fantail -- with large "forked" tails, flowing fins and an array of various colors. Goldfish do a great job cleaning up a tank but they produce a high level of PH so you need either a really good filter and / or constant water changes -- especially if you're going to have these in a tank. Velvet Red Swordtails are TROPICAL FRESH WATER FISH (Xiphophorus hellerii in family Poeciliidae of order Cyprinodontiformes). A live-bearer, it is closely related to the southern platyfish or "platy" (X. maculatus) and can interbreed with it. It is native to an area of North and Central America stretching from Veracruz, Mexico, to northwestern Honduras. Show Guppies are a FRESH WATER TROPICAL FISH. They only differ from regular guppies by being more colorful, beautiful, larger, more healthy and with more elaborate fin structures and cosmetic traits -- due to the careful intervention of humans. No chemicals or other harmful elements are used in producing show guppies. (Poecilia reticulata), also known as the millionfish, is one of the most popular freshwater aquarium fish species in the world. It is a small member of the Poeciliidae family (females 46 centimeters (1.62.4 in) long, males 2.53.5 centimeters (1.01.4 in) long) and like all other members of the family, is live-bearing. Guppies are native to Antigua and Barbuda, Barbados, Brazil, East Timor, Guyana, Mayotte, Netherlands Antilles, Trinidad ... https://www.youtube.com/watch?v=1k4xTKu7DwI