Given the time of year, one of the questions many aquarium and pet shops get from interested fish keepers is – “Which tropical fish can I keep without a heater?” Technically the answer to this is that no tropical fish can be kept without a heater. But the question from the fish-keeper was most likely meant to be – “Are there any non-goldfish that I can keep in an unheated aquarium?” The Temperate water fish are most popular during the cooler months as they are fish that may be kept in indoor, unheated aquariums in winter and also still thrive in the warmer summer months. Some of these fish are amongst the hardiest of all fish kept.
There are several fish that are commonly available in almost all pet shops around Australia that fall into the “Temperate” category.
Paradise fish were one of the first aquarium fish kept as pets. They were kept in Europe in the late 19th century and made their way to Australia in the early 1900’s. They were kept as pets in their native China many hundreds of years earlier. Paradise fish are one of the hardiest and most tolerant aquarium fish kept, tolerating temperatures much lower than many fish.
Also from China are While Cloud Mountain Minnows, often referred to as “White Clouds”. The White Cloud is native to an area in southern China but is now rarely found in the wild. Fortunately, there are millions of these bred annually in many parts of the world. White Clouds are the almost perfect beginner fish, being particularly tolerant of water conditions and temperatures. The White Cloud can tolerate water down to around 5 degrees Celsius.
Rosy barbs are one of the more brightly coloured and active aquarium fish. They are naturally found in cooler, flowing streams in India and Sri Lanka. The males of the Rosy barb are brightly coloured and are a beautiful and showy fish. There are several colour forms available including those with long fins, metallic scales and also several variants of the red colouration in the males.
Some of the other more cool-temperature tolerant fish include Peppered Corydoras Catfish, originally from cooler waters in Brazil, Variatus Platies from Central America and Zebra Danios, originally from India. The Zebra Danios are particularly interesting in that they have been used in lab research in cell regeneration experiments. They are known to have regenerative abilities unknown in most animals. It is possible that one day, there will be a cure to a significant human health issue that may be assisted from research on the Zebra Danio.
All of the Temperate Water fish mentioned in this article are commonly available in most Just For Pet stores around Australia. If you are looking at what to restock your tank with, all of these fish can be considered. They are generally hardy aquarium fish tolerant of a wide variety of water parameters and readily eat most aquarium fish foods.