Steve Andrews is a naturalist and tropical fish keeper with plenty of experience in looking after many species.
Can You Keep Tropical Fish Outside?
Many people assume that all tropical fish have to be kept in heated tanks at all times, but this isn't strictly true. Many of the hardier species can be kept and bred in outside ponds in the summer months in the UK, North America and other countries in the Northern Hemisphere.
As long as the fish are put out there after all fears of frost are over and brought back inside in the early autumn before temperatures drop too low, you will be surprised by how well many species can do.
Some tropical fish are actually quite well known for being able to live in cooler water. The paradise fish (Macropodus opercularis) and the white cloud mountain minnow (Tanichthys albonubes) are both good examples of hardier species.
Acclimate Them to the Outdoor Water Temperature Slowly
Of course, you need to get them used to the temperature outside by putting them in a container and allowing it to float for some hours to get to the same temperature. It is harmful to take them from warm water in a tank indoors and put them in cooler water; it will be too much of a shock to their bodies.
Paradise fish are one of the best-known fish sold as tropicals that can be kept outdoors in subtropical and temperate climates in summer. They come from the paddy fields, ponds and ditches of many parts of East Asia.
Paradise fish have attractive red and bluish stripes on their bodies as well as red on their fins. The males are larger, have bigger fins and are more colourful in general. They will fight with other males, so they are best kept only with females or with other fish of a comparable size. Even with fish their own size or bigger paradise fish of both sexes, they can often become bullies and will chase other fish and nip their fins. They will eat any small fish they can catch.
They were first brought to Europe in the 19th century long before heated aquariums were popular and available. Besides being able to survive in unheated tanks and outdoors in summer, paradise fish do not need much oxygen in the water because they are anabantids or labyrinth fishes, which are adapted to breathing atmospheric air that they gulp from the surface.
Paradise fish males construct nests of thousands of bubbles into which the eggs of the female go after they have been squeezed out of her in an embrace. The males become especially colourful when courting females and they extend and display their fins.
The interesting habits, colourful appearance and hardy nature of the paradise fish make up for the disadvantages of its aggressive nature.
White Cloud Mountain Minnows
The white cloud mountain minnow is another species that is sold and can be kept as a tropical fish but will also do well in unheated aquaria and in outdoor pools where it can survive in temperatures down to 41°F. It comes from China but is virtually extinct in the wild.
The white cloud mountain minnow is a small fish from the Cyprinidae of the carp family. It only grows to about 1.5 inches in length, but its small size is made up by its colourful appearance, lively behaviour, peaceful nature and the ease with which it can be kept and bred.
It has a red spot on the tail and a black line down its body. White cloud mountain minnows like to live in shoals and look more attractive this way as they swim happily about. They scatter their eggs amongst water plants, and the baby fry can be safely left with the parents because they will not get eaten.
Other Tropical Fish That Can Be Kept Outdoors
I have personally found that tropical fish I have transferred to outdoor garden ponds in summer have often done better than those in the house in heated tanks. They are able to get a wide range of natural foods when out in an unheated pool.
Species of live-bearers I have kept outside include:
- Guppies (Poecilia reticulata)
- Platies (Xiphophorus maculatus)
- Black Mollies (Poecilia sphenops)
- Swordtails (X. helleri)
These fish are all sold as tropical fish, but come from subtropical southern States in North America and from parts of Central America. Live-bearers are species of fish that as their name suggests, give birth to living young instead of the usual egg-laying method of reproduction of the majority of fishes.
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Platies and Guppies
Platies and Guppies are often seen in ponds here on Tenerife where I am currently living. This island is classed as subtropical too. Mosquito Fish (Gambusia affinis) are seen in thousands in ponds and reservoirs here as well. This is yet another live-bearer that can and does thrive in many subtropical parts of the world and can stand cooler temperatures.
I have also kept the definitely tropical killifish Aphyosemion gardneri, or Fundulopanchax gardneri as it is also known, outdoors in summer and in unheated tanks in the house. I say it is definitely a tropical fish because it comes from Nigeria in Africa.
It is thought of a 'specialist fish' because as a killifish, it has eggs that are laid in the substrate and need a period out of water in damp peat to mimic conditions in the wild where the streams and ponds would dry up. It is what is known as an 'annual' or 'bottom-spawner' because of this. Such species only have short lives in the wild because the water dries up and they have developed a method of keeping the eggs safe unto when the rains come again. Aphyosemion gardneri, in my experience, also survives in unheated tanks and can be kept in garden pools in summer.
Tropical Fish at Subtropical Temperatures
There is certainly a lot of room for experimentation with tropical fish to see what species can live in cooler water. With many, it seems they can do so. Just because a fish is sold as a tropical fish doesn't mean it cannot live at subtropical temperatures.
Questions & Answers
Question: I need fish that can tolerate temps around 80 in my outside pond?
Answer: It would help if I knew where you are located but Paradise Fish would probably be suitable for this because they tolerate a wide variety of temperatures. Mosquito Fish can also do well at a high temperature and are very adaptable. Many tropical fish species can be kept outside in summer but if you are in an area where you can expect cold and sub-zero winter temperatures the fish will not survive and need to be brought in from autumn through till late spring, depending on the average temperatures where you live.
© 2011 Steve Andrews
Halemane Muralikrishna from South India on August 16, 2019:
Nice photos. You may like to see fish life in mangroves.
Steve Andrews (author) from Lisbon, Portugal on December 20, 2014:
I should take them inside in case they die when it gets too cold.
hello on December 15, 2014:
I kept Zebra Danios outside in northern UK! I put them in a 2 foot green tub in June and they are still surviving. The UK winters can get very cold.
Steve Andrews (author) from Lisbon, Portugal on April 22, 2014:
I am glad they are OK. Thanks for commenting!
betta fish rule on April 22, 2014:
I have two male paradise fish because the pet shop said one was a male but both fish have been fine for over a year and have never nipped at each other
Steve Andrews (author) from Lisbon, Portugal on November 18, 2011:
Thank you, Chasing Ridley and Denise! Good luck with the challenge, Chasing! Most of mine are going to be on fish I think!
Denise Handlon from North Carolina on November 18, 2011:
Beautiful photos to go along with the interesting facts. You are so knowledgeable about this subject. Rated up.
The Evolista from Los Angeles on November 17, 2011:
Interesting hub! It makes so much sense that some of the fish would thrive outside during the summer. I'm doing the hub challenge too. I look forward to reading your hubs.