Aquarium fish do not always have to be kept in heated tanks under totally controlled environments. Many native fish of temperate and sub-tropical climates are species of tropical fish, which can be kept and will thrive and breed in outdoor ponds if certain conditions are met.
1) The average temperature is consistently over 60 F and average air temp is over 70 F in the day time.
2) The pond is at least partially submerged in the earth, which “normalizes” the average temperature within the body of water.
3) The pond has sufficient plants so the fish can seek shade from the intense summer sun.
4) The water level is kept up with either rain water or aged water, not directly from a garden hose
5) Grass clippings are not allowed to fall into the pond, since this risks cross contamination by pest control substances or fertilizers that could poison the fish and plants in the pond.
6) Until the fish are established in nature, feed them once a day with general fish food, similar to what you would feed them in an aquarium.
7) Relax its easier than it sounds.
As long as tropical fish are put outside in ponds and fountains of sufficient depth after all fears of frost are over and brought back inside early in autumn before temperatures drop below 60 F many species can thrive in the summer ponds of temperate and subtropical climates.
Some of the oldest varieties of aquarium fish are called tropical fish but come from more temperate climates, and survive very nicely in unheated aquariums. The Paradise Fish (Macropodus opercularis) and the Whitecloud Mountain Minnow (Tanichthys albonubes) are good examples of heartier species of tropical fish that do not need the warmth that an Angle Fish needs, for example.
Goldfish and Koi have long been good pond fish, since they can even handle the icing over of water as long as liquid remains below the surface. But Goldfish and Koi are not effective in controlling mosquitoes, and tend to be a dirty fish requiring much more maintenance and filtration than smaller aquarium fish.
Naturally all fish, even goldfish must be properly acclimated to outside pond water. If the pond is long established, and mature, it is a good idea to make a bucket of ½ pond water and ½ aquarium water and let the fish get use to the “natural” outdoor water for a few hours. Whether or not you do this acclimation; you must put any fish in a plastic bag of their water and float it in the pond to equalize the temperature for at least 15 to 20 minutes before releasing the fish into the pond or fountain.
The fish we are describing are the heartiest of aquarium fish and will survive just about anything. One thing you must look out for are predators, larger fish like Goldfish and Koi may be attacked by cats, raccoons or even passing birds of prey. The smaller aquarium fish like guppies, platies, swordtails and mollies are so prolific however, that their constant flows of fri will outpace just about any predator, another great reason to try these mosquito eating marvels.
Keeping outside summer ponds free of mosquito larva, clear and active does not take harmful chemicals. A firm like Florida Pond Management can help you convert a stagnant body of standing water into a show piece with fountains and fish, free of insect larva and odor free in a few easy steps. Try it the natural way, fish, live plants and aerated water is now nature intended healthy bodies of water to maintain their clear beauty.