There are many distinctions to be made between the different types of home aquariums. Not only can fish tanks be divided between freshwater and saltwater but they can also be tropical or coldwater environments. Coldwater fish tanks are typically unheated, which allows for water temperatures to fall into the sixties. Only certain species of fish like goldfish, tetras, and danios are suited for this type of environment; most tropical fish require warmer temperatures to thrive.
Goldfish and Koi
Goldfish are the fish that are most commonly recognised as coldwater fish but koi, a related species, are also coldwater fish. Goldfish and koi do not require heated water which is why they are popular for use in outdoor ponds. Though goldfish and koi are great for coldwater tanks and do not require much maintenance, they can grow to be very large and should be kept in tanks no smaller than twenty gallons in water volume.
Guppies are well-known for being hardy fish that are great for beginners. Not only are guppies tolerant of varying water quality but they also do well in unheated fish tanks. Most guppies only grow to between one and two inches in size so they do not require a great deal of space. But they tend to reproduce rather quickly, so you may need to provide them with extra space. Guppies come in a variety of colours and they are a way to add colour to your coldwater tank.
There are many varieties of tetra and several of them do well in water temperatures as low as sixty degrees. The bloodfin tetra and the Beunos Aires tetra can be found readily in pet stores, and they tolerate colder water temperatures than most freshwater tropical fish. Most tetras do well as community fish and they prefer to be kept in groups of at least four of their own kind. Tetras get along well with most community fish but some species, like the Beunos Aires tetra, tend to eat live plants so exercise caution when adding them to a planted tank.
There are several types of danio including zebra, leopard and pearl danios, and even among these types there are large-sized and long-finned varieties. Most danios are capable of withstanding colder water temperatures in the mid sixties and do quite well in community tanks. Zebra and leopard danios thrive best in schools, but their larger relatives, pearl danios, do not have this requirement. Danios are a hardy species that are very easy to care for and great for the beginner aquarium hobbyist.
White cloud mountain minnows are another species of fish that are recommended to beginners because they require very little care. In addition to being easy to keep, white clouds can withstand cold water temperatures. The variety of white cloud found most commonly in pet stores are silver with a white horiztonal stripe and a red tail, but a golden variety is becoming increasingly popular. Though white clouds can live in coldwater tanks, lower water temperatures may decrease the vividness of their colouration.