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Basic Considerations for Ponds

Considerations for Frog Ponds in the Tropics

As more and more people move to Far North Queensland, there is increasing pressure to remove habitat and replace it with houses. This is still one of the leading causes for frog decline in this region. It does help frogs if microhabitats can be provided for them so that they can still have places to live and breed whilst having to share that space with humans. This page covers the basics of setting up a frog pond in our tropical climate.

If you are outside Australia, please be aware that the suggested techniques and references to keeping toads out of ponds only pertains to areas where the introduced cane toad (Bufo marinus) is a pest. Australia has no naturally occuring toads so any and all attempts to exclude toads are against the cane toad. If you live in the US or Europe or Asia, you don't want to exclude your own local toad species from your ponds. In fact, many species of toads are endangered and these are species you would want to help - not exclude!

The Pond Itself

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The larger in surface area the pond is, the wider variety of species that will use it for breeding. However, if all you can manage is a small pond - even one of those fiberglass kits available from the garden shops - this will still help the frogs because they need a reliable source of water during our dry season (and especially when we are in drought periods!).
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It is best if the pond is at least 30cm deep and preferably 40cm or more because of evaporation and heat - especially if the pond receives more than a couple hours sun each day. Please check with your council about any regulations they might have concerning fencing. For heavily shaded areas, you can get away with plastic kiddie ponds which are only about 20cm deep at best but the pond will still need at least a 1/2 hour of sunlight to work.
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Do NOT use tap water from the hose to fill your pond - there are ways to get rid of the usual chlorine that is added to tap water but many councils are now adding fluoride to the tap water. Based on our own experiences since fluoride entered the local water supply in December 2010, and some reports from others who rescue tadpoles, fluoridated water can kill tadpoles outright but it also appears to weaken their bones to the extent that they can't climb out of the water and drown. Of course, proper scientific study could prove this but somebody has to fund it! See comments below about fish in ponds for the REAL damage that fluoridated water does!
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The pond should receive shade for most of the day so that the water doesn't become too hot, but an hour or two of sunlight is needed for plant growth, tadpole development, and to warm up the water a little bit.
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The pond can be dug into the ground or it can be a container sitting on top of the ground and surrounded by a decorative wall or stone, wood, tiles - whatever you like. If an in-ground pond is built and you want it to be used for breeding, there should be one side with a sloping surface which will allow ground dwelling frog species to "walk" out of the water when they are ready to metamorph.
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A small water fountain or pump will provide oxygen for tadpoles and fish in the water (as well as look lovely) but a fountain is not necessary for the frogs and should be shut off at night.
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Because of the arrival of contagious diseases which might require the draining of the pond during a certain time of year or disinfection when sick frogs have been in it, it is good if you have a ready-to-use easy system of draining the pond into the toilet or sink. This can be purpose built into the bottom of the pond when constructed or you can have a hose and pump available to direct the water into your household grey water system. If you live in an area which has experienced an outbreak of chytrid fungus or viruses, it might be advisable to drain your pond for disinfection or to drain your pond during the winter months (to control chytrid). If you are unsure whether either of these diseases has been a problem in your area, you can contact your local frog conservation group or the nearest college or university with a biology program or a museum.

A new threat to frogs: fluoridated water!

If you live in the tropics, you are required by law to keep fish in your water bodies to control mosquitos. Small species of fish with small mouths (e.g., basic guppies, Pacific Blue-eyes, white clouds) are the way to do this when you want frogs to breed in your pond. However, since the Queensland state government mandated that fluoride is to be added to the water supply (this started locally in December 2010), we have seen three major changes to small fish species:

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They don't thrive and die within days to weeks, even when kept in rainwater after arrival
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They don't reproduce
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Once being safe for frog ponds, they have turned into carnivorous predators, devouring eggs immediately and killing young tadpoles (even when the fish are fed daily with fish food)

This situation with fluoride affecting small fish is a major problem for frog ponds and becomes yet another cause of frog decline by preventing recruitment. Even if your pond is entirely rainwater and never topped up with the hose, the fish could have been bred by or resold by aquariums that are using fluoridated water. Because the fish don't stay very long at a seller's facility, the mortality rate might not be noticed or reported back to the seller. The customer (you) buys the fish and they die soon after without breeding, but you may not bother complaining to the shop, thinking that it was your fault the fish died. (This has been a recurring theme with many small animals that are in the trade.)

To provide "safe" fish for your frog pond, you will need to ask aquariums about their water supply and the water supply of their suppliers. The fish will need to come only from suppliers with their own reverse osmosis setups and you will need to avoid using tap water to fill your pond. Rainwater, pure water brands from the shops, and your own reverse osmosis water filter (domestic filters should run about $400-$500) are acceptable for your frog pond. (You can also write to the authority in your area who requires fluoridation to complain - this policy is bad for your health as well as being bad for frogs.)

Update: QLD government turned tail on the fluoridation law and has now left it up to individual councils to fluoridate or not. Thankfully for this region, Cairns, Cassowary Coast, Douglas and Tablelands councils have all voted against fluoridation. There are now ten councils in QLD (as of this writing that have abandoned this controversial practice but sadly that is not the situation in southern states or overseas.

Cane toads

Frog ponds are supposed to be for frogs but if you have one, the toads will happily use it. There are three ways to keep toads out of the pond: one is to make it an above-ground pond at least 60cm high with vertical walls (but some frogs don't favour these setups), and another is to put the pond in-ground but exclusion-fence off around the pond or yard and remove the toads still inside. The disadvantage of the above-ground pond is that it will be used by the tree frogs only so the ground dwelling frogs miss out. The third (cheaper) way is not to barricade the toads out but to remove the toads and their eggs regularly.

If you want to provide a physical barrier to toads with a dug-in pond, you merely need to provide a solid barrier which extends several inches down into the soil and reaches about 60cm above the ground. For example, a chain link or tubular pipe fence can have shade cloth attached and low shrubs or heliconias can be planted to hide the shadecloth. More information on this is in our Toad Exclusion page. If neither an above-ground pond nor a fence is possible, then a regular vigilence on the pond to remove toad eggs is the next best option. (See our pages on Toad Eggs and Humane Disposal)

Around the pond

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There should be ample vegetation around the back of the pond and throughout the yard. Combine plants with a variety of leaf shapes and densities so that shelter and perching spots can be used by frogs of various sizes.
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Having a source of water and shelter is only one part of the picture - another is a source of food. To encourage bugs into the yard, do not use any insecticides around the home or property, incorporate a compost pile into yard somewhere, and leave a small lamp/spotlight on in the yard for part of the night to attract moths. Planting natives which attract moth and butterfly caterpillars will also help.
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Having a lovely microhabitat for frogs isn't going to help much if predators pick off the frogs. Predators can be native species (which is a natural part of the food chain) but serious introduced predators are dogs and cats. Not only do cats attack frogs but they carry parasites which are deadly to frogs (read about this in our special threats page). If you are trying to keep out your neighbours' cats, you can add netting to the top of a fence. We've been told that smearing crushed chillies onto the fence is also supposed to have a repellant effect on cats. There may be other plants that can be planted along the perimeter of your yard to keep out other people's cats - check a companion planting gardening guide for any possibilities.
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If you have dogs or cats yourself, you can restrict their access to the area around the pond and allow the dogs run of another part of your property. Many people don't believe that dogs find frogs but they do - we see the results at the Cairns Frog Hospital. Dogs usually find the sleeping frogs during the day (we suspect they probably smell them). Cats are best kept indoors at night as frogs are not the only wildlife they prey upon. Cats hunt by instinct - not personality - so what might be a quiet, passive cat inside your home could easily become a successful hunter once let outside. One way to find out what your cat does away from home is to ask your neighbours!
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Kids love frogs and this is a great thing, but don't let them run around the pond or jump around in it. Breeding frogs hiding in the plants could be injured or killed and tadpoles might be crushed or splashed out onto the ground. Supervise your children when they want to have a look at the tadpoles or observe nighttime breeding activity of the adults.

Water quality issues

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In the tropics, it is essential that mosquitoes are controlled. However, putting just any fish in the pond may completely negate the frogs' ability to breed there. Fish should be added but only use smaller fish which have a small mouth (see above for comments on the effects of fluoridated water on small fish). The most commonly used native is the Pacific Blue-eye. Non natives can be used if you are in an area where sick frogs have been found or you have had diseased tadpoles previously - the exotics to use would be the smallest guppies or White Clouds. The reason for chosing exotics in a disease prone area is that if you should have a batch of diseased tadpoles in your pond, you'll need to drain and disinfect the pond before another batch of eggs turns up. Everything in the pond at that point will need to be destroyed - so to avoid having to kill native fish, the exotics are a little better. Avoid Goldfish, Empire Gudgeon, Rainbow fish, any species which has a reputation of eating its young, and any larger species of fish.
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If you want to increase the number of fish in your pond, get a mixed batch of male/female or at least one pregnant female. If your pond is really small and you don't want more fish than you can handle, just get fish of either all male or all female.
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We have started getting lab results (as of Dec 2003) of ciliated protozoa attacking tadpoles and metamorphs from some ponds where soil has washed into the pond. Please keep soil out of your pond and if you have a silt problem already, it would be best to drain the pond and clean it thoroughly and start again with fresh water.
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If you have tadpoles in the pond but not much algae or aquatic vegetation for them to eat, you will have to provide food for them or they will eat each other. See our raising tadpoles page for more information about feeding. Don't overfeed as the water will become fouled.
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Also if you have tadpoles and not enough submerged, leafy vegetation, you will need to supplement their oxygen supply or they will suffocate. If you have seen tadpoles hanging vertically from the surface of the water, this is a sure sign that there is not enough oxygen in your pond. A pump or aerator running for a few hours a day should fix this problem unless you go for underwater plants.
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Sometimes pond owners report that everything in their pond dies suddenly (including the fish). This is often the result of a dead cane toad falling into the pond. Some native birds and rats have learned how to eat the toads without accessing their poison glands. They leave behind the head and skin at the edge of the pond and, if these body parts fall into the water, everything is poisoned. If this should happen, the entire pond needs to be drained, rinsed out and filled with fresh rain water.
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Another cause of pond life dying is the use of chemicals in the yard. Avoid this around the pond and anywhere upwind/upstream of it. If chemicals should get into the pond, it will have to be drained and cleaned, as above.
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Sometimes diseases will kill tadpoles and they will die in large numbers although the fish appear okay. In particular, there is one new disease that has turned up in Australia that affects tadpoles very strongly - see the Disease section, Virus Which Causes Sudden Death and Deformities page. If the pond seems fine but dead or deformed tadpoles are being found, contact us to discuss it. If you are in this area, the remaining tadpoles might be turned in so that they can be tested. If the tadpoles die but the fish don't, the pond might need to be drained and disinfected. (If you are on a septic system, this will be difficult because chemicals are used to rid a pond of disease which can't be put down the toilet.) Once drained, use bleach to scrub all surfaces in the pond and rinse this very well two or three times. Then use betadine (10% povidone iodine) sponged liberally over the pond liner for at least five minutes, then rinse thoroughly, disposing the rinse water in the sink or toilet (in sewerage areas only, for septic system areas, leave all the rinse water in buckets in the sun until the water gets clearer and then pour onto a driveway or other non-vegetated space). Let dry out completely for a day or so and then fill with clean rainwater as above. The remaining live tadpoles can be dropped in to us so that we can document their symptoms and possibly get them tested if they continue to expire.
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Snails should not be encouraged in ponds - they can carry the larval stage of a flatworm parasite which attacks tadpoles. If you are in the US, you should ensure that all snails are removed as soon as they are noticed and if you obtained your tadpoles from a petshop, please contact them to let them know that all snails should be removed from their tanks asap.

Frog ponds are one of the best ways to help restore frog populations so we hope you'll want to put one on your property soon! Please contact us if you have any questions that haven't been covered in this page.

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Before You Collect Those Tadpoles

Raising Tadpoles in Containers and Ponds

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