If frogs are to breed: they need water.
A pond or a container filled with aquatic plants like water lilies can add a new dimension to your garden. It could also add a whole new dimension to your property, attracting a range of wildlife, and particularly frogs.
For a frog pond to work it needs to have a local natural source of frogs (taking wild frogs for your frog pond is illegal and can spread disease). If you occasionally hear or see frogs in your yard then build a frog pond and they will come!
Managing your mosquitoes
If you are building a frog pond or putting containers of water into your garden to grow aquatic plants you will also be providing a breeding site for mosquitoes. While frogs and dragonflies will feed on mosquitoes you can also add native fish such as blue eyes to your frog pond to prey on mosquito larvae (these fish may also eat some of your frog eggs and smaller tadpoles). Mosquitoes usually lay their eggs in shallow, still water so installing a pump to improve water flow will aerate your water and also deter mosquitoes. Some aquatic plants like water lilies prefer still water so installing a water pump may affect your choice of plants for your pond.
Where to put a frog pond
Frog ponds need to be sited where they can get morning sun but be shaded during the middle of the day (aim to have part of your frog pond in the shade at any time). This may mean that you have to provide shade planting when you put in your frog pond.
You also need to consider how close the pond is to a bedroom window (both yours and your neighbour’s) as some frogs call loudly and persistently throughout the night. If you plan to install a water pump you may need to have access to electricity (solar powered pumps are available). You may also consider a solar powered light. This will attract insects and become a focal point for feeding frogs—and allow you to watch them at the same time.
Before any digging starts, mark out where the frog pond will go and make sure you are happy with its location and how it fits in with the rest of the garden space (it will be far easier to change your mind now than when it is fully installed).
Avoid placing your pond directly under trees to avoid excessive leaf fall.
What to make a pond out of
Ponds can be made out of anything that will hold water—old bath tubs, wading pools, or styrofoam boxes.
Plant nurseries and landscape suppliers sell prefabricated ponds made of plastic or fibreglass. A sheet of pond liner can also be used to create your own pond exactly to the size and shape that suits your backyard.
Pond size is largely a matter of personal choice, available space and practicality. Frog ponds should be shallow around the edges gradually deepening to a maximum of 60–70 cm (ponds can be shallower if required). The varying water depth creates a range of water temperatures and allows tadpoles to retreat to cooler water when it is hot, and deeper water when disturbed.
Fitting out and filling your pond
Seek advice on installing prefabricated ponds and PVC liners from the plant nursery or landscape supplier when you buy them (they will also advise you on selecting and installing a water pump and lighting that best matches the size of your pond)). The bottom of the pond should be covered with 3–4 cm of river sand or gravel to hold the roots of aquatic plants. Larger plants can be kept in individual pots. The surface of a submerged pot should be covered in a layer of river gravel to stop soil washing out of them. Plant nurseries can also advise you on what plants to use in and around the pond.
Planting out your frog pond will be a matter of personal choice while still providing shelter and shade for the frogs living there. Be prepared to move plants and select new varieties to create the most effective frog habitat and the desired ‘look’ for your garden at the same time. Remember that the plants will also need to provide habitat for a range of insects. As a general rule aquatic ferns like azolla and duckweed should be avoided as they are environmental weeds and can be spread to other water bodies on the feet of birds.
The pond should also contain rocks and logs to provide additional shelter, basking sites and safe places for new frogs to emerge from.
Water quality is also critical for a healthy frog pond and ideally rainwater should be used. If you have to use chlorinated water it should be left to stand for 5–7 days before it is used to fill a pond (or fill the pond and keep frogs out of it for this length of time). You should also avoid using fertilisers and sprays near the pond that could drift onto the water surface, and position your pond so it doesn’t receive runoff from the rest of your garden or lawn after heavy rain.
Tap water from a treated town drinking water supply may not be ideal for fish and other aquatic animals. If you are concerned about using tap water in your frog pond, you could consider topping up your pond with rainwater, ensuring your frogs have access to natural sunlight and providing additional dietary calcium via natural frog food or dietary supplements.
The pH of the water should be checked regularly to ensure it is as close to neutral as possible. pH measuring kits are available from pet shops.
Aquatic plants should be thinned out to ensure they do not cover more than a quarter of the pond surface.
Algal blooms can also occur in frog ponds. These blooms occur when the nutrient level in the water is too high. Blooms in an isolated pond should eventually die off as the algae consume the nutrients. If the algae persist, it should be removed along with any nutrient source (e.g. decaying leaves). Excess dead leaves and old uneaten food should be removed as part of the general maintenance of the pond. Care should also be taken to avoid nutrient runoff from the surrounding lawns and gardens.
The presence of mosquito larvae in the pond will also need to be monitored and kept in check through a range of natural control measures. While the frogs will eat mosquitoes, you can also introduce some native fish to your pond. Native fish may also eat some frog eggs and smaller tadpoles.
Microbats are also effective mosquito predators and you may consider installing a microbat box in a tree near your frog pond.
Frogs are affected by Chytrid fungus. The best way of controlling the spread of this fungus is to treat your frog pond as a quarantine area by not bringing in any material that could be infected. Frog ponds should only be populated by frogs that have moved into the pond by themselves or have been collected on your property (frogs can only be collected and kept on the same property by the property owner). If you do want to keep frogs, the following rules apply:
- the frog must be classified as ‘least concern’ under the Nature Conservation Act (use the Wildlife online function and create a species list of your local government area to find out which species are ‘least concern’—these are indicated by a ‘C’ for common in the column showing their classification)
- no more than 8 frogs can be kept with no more than 2 frogs of the same species (this does not include tadpoles)
- if the frog produces young the offspring must be released into the wild within 7 days of the tadpoles becoming frogs.
For a full description of the legislation relating to the keeping of frogs see section 50 of the Nature Conservation (Wildlife Management) Regulation 2006.
Avoid handling frogs. Frogs have sensitive skin and can readily absorb chemicals from anything they come in to contact with, including your hands. Your frog pond should give you many opportunities to observe frogs closely without having to handle them.
Thinking outside the pond
While a frog pond will become the hub of activity for wildlife in your backyard, the pond’s surroundings also make up an important part of the frog’s habitat. The area surrounding one side of the pond needs to provide a sheltered and moist refuge area for young frogs emerging from the pond. The substrate could include moist river gravel and leaf litter for burrowing frogs to hide in. You may also want to build a garden up to one side of the pond to provide a safe mini-wildlife corridor between the pond and other parts of your garden. This will make it easier for insects and other wildlife to use the pond.
It is important to ensure your frog pond doesn’t pose a safety hazard for young children. If this is a concern, ponds can be fenced or covered with mesh. Ponds can also be kept shallow with gently sloping, non-slip beds.
If you have cane toads in your area keep an eye on your pond to make sure they don’t take it over. Surround your pond with dense border of plants such as lomandras or erect a 50 cm mesh fence to keep toads out.
Remove cane toad eggs. They are laid in water in long strands of black eggs surrounded by clear jelly (a female can lay up to 35 000 eggs a year). Cane toad tadpoles are very dark, their tails are short compared with their body size, and they tend to cluster together. Cane toad tadpoles can be removed by netting and then placed in a water proof container and frozen.
The most practical way to kill cane toads is to place them in a container (with air holes) and cool them down in a refrigerator until they become dormant. Then place the toad in the freezer for several days. There is some evidence that a cane toad can still feel pain after it has been in a refrigerator (at 4 degrees) for an hour. Therefore a toad should be cooled down for as long as possible before being placed in a freezer to minimise the likelihood of it feeling any pain when it is frozen.
The dead toad can be disposed of by burying them or putting it in your wheelie bin (on the day it will be emptied).