What fish are good for a fresh water pond in tropical Australia?

Answer 1

Given that for the majority of people purchase from an aquarium shop is the only practical alternative, there are only limited choices.

The crimson spotted rainbowfish Melanotaenia fluviatilius is a good choice for many areas of Australia and is often available through the aquarium trade. Of the many species of rainbowfish, this one has the best low water temperature tolerance and is actually found in the wild as far south as the Goulburn River in Victoria. In tropical areas, practically any species of rainbowfish would be suitable. Rainbowfish eat mosquitoes, ants and other small insects as well as algae and make an ideal pond fish. In an established pond they may not even need supplementary feeding if the stocking rate is kept low. In Melbourne I have kept one of these fish in a smallish pond (about 120 x 90 cm x 45 cn deep) that is protected from frost for over six years without any additional feeding and the pond has remained mosquito free the whole time. More recently (Dec 2005) I have set up a larger pond (5.5 x 3 m x 50 cm deep) and have stocked it with two male crimson spotted rainbowfish which have proven to be excellent at mosquito control (it was full of mozzies when I added the fish) and since then we have had succesful breeding of eastern banjo frogs Limnodynastes dumerili in the pond and tadpole survival does not seem to have been effected.

Another fish commonly available through the aquarium trade that makes a good pond fish in warmer areas (eg Sydney and further north) is the Southern Blue-eye Pseudomugil signifer (also known as the Pacific blue-eye). These attractive little fish are recognised as voracious mosquito predators and are native to the east coast from North Queensland to as far south as Narooma.

Autralian smelt are an excellent choice for much of south eastern Australia for mosquito control and have the added advantage that they are very frog/tadpole freindly. These fish are now becoming available through the aquarium trade and will breed in most ponds providing sufficient suitable habitat is provided in the form of aquatic vegetation and other structure in the pond.

Other fish that are sometimes availabel from time to time are various species of pigmy perch and galaxias. The pigmy perch are more likely to be more of a predatory threat to tadpoles, but if you do not have frogs in your area they couold be an excellent choice and will breed in most situations. Most salaxias species when they are available are suitable but these species are often "annual" fish and will not breed in a pond, but are a safe choice to keep with frogs/tadpoles.

If purchasing any of these fish, ask if they are cool water adapted, as some will have been kept in tropical aquaria for use in home tropical tanks. If the fish are not cool-water adapted, you can do this yourself (this is best done during the warmer months when your pond temperature is at its highest. First assess how much of a water temperature difference thee is between the fish you have purchased and the pond. If it is less than 2-3°C then simply float the bag containing the fish you have purchased on the pond, out of the sun, of course, for an hour or so until the water temperatures have equalised, then open the bag and let your fish swim free. If the temperature change is more than that you need to reduce the temperature of the fish more slowly to allow them time to adapt. A medium sized "esky" is ideal for this purpose, half fill the esky with water at the same temperature as you have brought the fish home in and use the correct amount of anti-chlorine chemical to make it safe (this can be purchased at any good aquarium shop). Release the fish into the esky and then allow the water to gradually cool over a day or so until it has reached the same as that of the pond. Once the temperature is correct you can release the fish.