Pond FAQ's
Author: Aqua Gardening
Date: 13 July 2022

Pond FAQ's

If you're planning a pond or if there is something not quite right with your feature pond or fish pond, check our Frequently Asked Questions below to see if we have the answer. If not, feel free to contact us for some free - and local to Brisbane - advice.

What's a good location for my pond?

The overall health of your pond will depend on its location. If you want to maintain it for several years to come, you should choose the location carefully. Keep the following considerations in mind:


Aquatic life in the pond will require some exposure to sunlight. Plants and fish will thrive if the pond is exposed to the sun for a few hours during the day.


Run-off is a big concern because it can actually kill the plants and fish in your pond. Run-off is water that flows off your landscape and backyard into your pond. This water will carry fertilisers and pesticides with it and that can harm the aquatic life.


If there are trees overhead, they can block sunlight from the pond and create dark areas. A few small trees with some shade won't have much impact on the pond. In fact, small shade would help keep the water clear of algae. But a big tree that provides plenty of shade will block sunlight and create an unhealthy environment.


You should be able to enjoy your pond so it's a good idea to choose a location with good visibility. Just make sure that the pond is visible from your home or patio.

How deep should my pond be?

That's a good question. Most people don't realise that the depth of the pond can have an impact on its health. Shallow ponds are easily influenced by changes in weather and evaporation.  The temperature and the pH levels do fluctuate quite a bit in them. Deeper ponds aren't influenced by the temperature variations outside the water and provide a more stable environment to the fish and plants. The depth depends largely on the region and the kind of fish you plan to keep.

Australian pool regulations

In Australia, a depth of 30cm or less does not come under the statutory requirements of a swimming pool. This means it will not require a pool fence. Such a pond can easily sustain plant-life and goldfish. A pond of this depth isn't easily influenced by the fluctuations in weather.

In cold areas

If you live in cold areas, we recommend finding the frost depth of your region before you install a pond. Your pond needs to be deeper than the frost depth to help your plant and animal life survive the winter temperature.

For keeping Koi fish

You need water of at least 1 metre if you plan to keep Koi fish in your pond. They're more vulnerable to fluctuations in temperature and deep ponds are more stable.

My pond just turned a toxic shade of green! What does that mean?

The water itself isn't green. In fact, if you remove some of the water and look at it, you'll notice that it's relatively clear. The green color is from microscopic algae that float freely on the surface. You see these algae often in a newly installed pond because the plant life hasn't taken root yet and the ecosystem of the pond is unbalanced. You will also see green water during spring until the plants begin to grow once again and the ecosystem is reestablished.

However, if you continuously have algae in an established pond, it's a sign of a grave imbalance. There are too many fish and organic matter and too few plants. You need to correct this imbalance to keep your water clear and free of algae.

How do I deal with algae?

There are several ways to deal with algae in your pond. You can install a UV clarifier along with your biological filtration system. That would keep your pond free of algae for a long time. However, you can keep algae at bay without the clarifier as well. You have to consider the causes and use the right solution.

Plant more plants

Lack of competition from aquatic plants is usually the cause of excessive algae. You can correct this by planting more plants.

Reduce sunlight

Sunlight tends to encourage all forms of life, including algae. You can prevent this by planting some floating plants. They will provide some shade to the bottom of the pond and prevent excessive algae.

Use an algaecide

An algaecide such as Algaefix kills algae but does not hurt fish or frogs. Ensure there is plenty of oxygen available to the fish if using an algaecide as the dead algae depletes oxygen from the water quickly.

Why is the pond water muddy and cloudy?

This is a clear sign of your filter and pump has malfunctioned. Before you pick the phone to call a professional, try to clean the filter. All you need to do is remove the filter and wash it with pond water. You don't need to do anything else or use any other cleaner. If the problem persists, try to clean the pipe with a brush. That should take care of the problem.

My fish are dying! What do I do?

No one wants to be confronted with a pond of dying fish so we understand your concern and urgency. There are some quick steps you can take to address the problem:

Increase the amount of oxygen

The lack of oxygen is most probable cause of fish deaths. You can address this by reducing the amount of algae in your pond and add plants like duckweed to it. These plants improve the levels of oxygen in the water, which benefits plant and aquatic life.

Reduce the amount of fish

Your fish will struggle to survive in an overpopulated pond and eventually die. We suggest that you limit the population to one large fish per 60 cm squared of space. So, you shouldn't have more than 25 fish in a 3m square pond.

Check the water quality

Fish are delicate beings and fluctuations in water quality can have an impact on their health. If you pond has high levels of chlorine, they won't survive. We suggest you check the water quality regularly and purchase a de-chlorinator for your pond, such as Pond Start. You'll find instructions on the package.

Do I really need a filter for my pond?

Your pond requires a delicate balance of plant life, animal life, sunlight, nutrition, and oxygen. All these elements work together to create a healthy ecosystem within the pond and this sustains your fish. It's very difficult to strike this natural balance because all of these elements have to be in place. A filter is a shortcut and helps you keep the pond clean, oxygenation, and free of algae. See our range of pond filters here.

How do fountains oxygenate a pond?

Almost everyone knows that water is created from two gases; hydrogen and oxygen. Water will automatically draw oxygen from the air and replenish that element. For that, it needs to be in contact with air. When the water is still, only its surface is in contact with air. While the surface gets replenished with oxygen, the water below doesn't have access to it. The fish consume oxygen present underneath the surface and eventually the levels drop.

The fish also produce byproduct gases like carbon dioxide and hydrogen sulfide that need to escape. Unfortunately, they get trapped under the surface and can't escape. This turns the water stale and unhealthy for aquatic life.\n\nA fountain introduces movement into the water. As the water circulates through the fountain and is sprayed in the air, it absorbed oxygen. The gas is constantly replenished as water comes in contact with air. The movement also allows carbon dioxide and hydrogen sulfide to escape. This keeps the water in the pond healthy and oxygenated. It's vital to introduce some form of movement into water to disrupt the surface. This leads to a healthy pond system.

Why are plants great for a pond?

Ponds require a delicate balance to thrive. Today, we use things like biological filters and UV clarifiers to maintain that balance. However, you can achieve it naturally with the help of aquatic plants. While this process does take time, plants will help create an ideal environment for your fish. There are many other advantages of introducing plants in your pond, including:

Replenish oxygen

Like all plants, aquatic plants consume carbon dioxide and emit oxygen. They naturally replenish the amount of oxygen in the water. If you have the right number of plants in your pond, you can be sure that it would always be fresh and well-oxygenated.

Provide shelter for fish

Plants also provide shelter to your fish. Sometimes they would need to hide from the light and the sun and plants provide ample shade for that. They also provide shelter for the fish to breed and lay their eggs. Without plants, the fish won't thrive and stay healthy.

Discourage algal growth

Plants compete against algae for light, CO2, and nutrition. Just their presence is enough to discourage algae growth and keep the water clear. The shade by the plant also doesn't allow the too much sunlight to penetrate into the pond. That discourages algae growth as well.

As you can see, plants can be very beneficial for your pond but you need to pick the right plants.

What kind of aquatic plants Should I introduce into my pond?

There are many different kinds of plants that you can introduce in your pond. They're broadly divided into 3 categories:

Floating plants

As the name implies, these are free-floating plants that remain on the surface of the water. The roots don't attach to the bottom of the pond so these plants are definitely free-floating. The best examples of these plants are water hyacinth, water lettuce, water lilies, lotus, and water poppy.

Shallow water marsh plants

These plants are usually planted at the edge of a pond and aren't fully in water. The best examples of these are umbrella plants, water iris, and horsetail.

Submerged plants

These plants are completely submerged and are usually planted in pots and placed on the bottom of the pond. Submerged plants help maintain the health of the pond by consuming nitrates and carbon dioxide. They produce oxygen and keep the water clean. The best examples of these are fanwort, elodea or American waterweed, ludwigia or water purslane.

These plants will be an excellent addition to your pond and will help create a great environment for your fish.

How can I protect fish from birds?

Predatory birds are a major concern for pond owners. Naturally, these birds aren't going to stop eating fish just because they're present in your pond and not some natural lake. Fish like blue heron and cranes will dive in for a feast if you leave your pond open. Unfortunately, some of these predatory birds are endangered species and can't be harmed in any way. Thankfully, there are some solutions available to you:


You can place a net above the water on the pond. This is the safest and most common solution. There are special mesh nets available in the market that you can place on the pond. That would block access. Unfortunately, that will compromise the overall beauty of your pond as these nets are visible.

Deeper water

You can also make the pond deep. Herons and cranes need to stand in order to hunt for fish and a deep pond wouldn't allow that. This isn't a fool proof solution but it can be effective. Bear in mind, ponds deeper than 30cm may need protective fencing to meet regulations.

Bird scarers

Some commercial fish farms use bird scarers that are programmed to emit a loud noise every 5 or 10 minutes. Unfortunately, this sound doesn't just scare away the birds, but it can also disturb you and your neighbors. Most don't consider this a practical solution.

Water jets

You can use a powerful water jet that would race across the surface of the pond every 5 to 10 minutes. This disrupts the surface and startles the birds. Eventually they learn not to hunt in that pond. Birds find this very disturbing and won't hunt in the same pond again.

Keep some Swans

If you don't mind swans, you can add a couple to your pond. These birds are beautiful and vegetarian. They wouldn't harm the fish in any way but they'll keep other birds at bay. However, you need to keep in mind that swans will consume your water plants and eventually spoil the water. Unless you constantly supply fresh water to your pond, adding swans can lead to a little extra work.

Create hiding places

If your predatory birds can't find the fish, they won't eat them. You can create several hiding places for your fish so that they have place they can escape to when they sense a predator. While this relies on the natural instinct of the fish, it is effective. Floating plants and board PVC pipes will help conceal the fish from the predator's eyes.

How do I deal with sludge?

Small amounts of pond sludge aren't really a problem. But if you have too much, it can compromise the health of the plants and fish in a pond, so you need to address the problem. There are four ways to treat sludge and all of them are easy to achieve:

Prevent debris

Pond sludge is formed from debris like soil, and decaying biological matter such as leaves from trees, cut grass, dying algae, fish waste, and pollen. You can install a good pond net over the surface during fall and winter and trim dead or dying parts of plants inside the pond. This will take care of most of the sludge.

Physically clean the pond

You can use your hands, a fine mesh net, or a pond vacuum to physically clean the bottom of your pond. This will remove most of the sludge and keep your pond healthy. Contact us if you would like a quote for a professional to come and clean the pond and make sure your fish stay safe.

Aerobic bacteria and algae

Healthy amounts of aerobic bacteria in your pond will keep it clean. You might also want to preserve the slime algae present at the bottom of the pond. These biological components will help to combat sludge.


Oxygen is good for your pond and it keeps the environment healthy. If your pond is rich in oxygen, it will keep the aerobic bacteria and good algae healthy. It will also keep the fish and plants in your pond healthy.

What is the best way to clean a biological filter?

Biological filters are an essential part of your pond. They need to be cleaned properly in order to ensure a healthy living environment for your plants and fish. In order to make sure you maintain good aerobic bacteria in the filter, here is what you should do:

Switch off the pump

Switch the pump off before you remove it from the water. If you don't, you'll burn out the motor.

Remove the filter

Carefully remove the filters and examine them. You should try to develop a set schedule to clean the filter and you can determine that if you understand how long it takes to get dirty.

Rinse the fiter with pond water

Rinse the fiter with pond water, not hose or tap water. Tap water has added chemicals that kill bacteria. While these chemicals are added to kill harmful bacteria and make drinking water safe, they can also kill good aerobic bacteria present in the filters.

Leave some residue

Leave some residue in the filters as this will help to kick-start new bacteria growth.

What water depth should different aquatic plants be planted in?

There are three different kinds of aquatic plants; floating plants, shallow water marsh plants, and submerged plants. These can be planted at different depths. We recommend that you consult with professionals about the ideal depths of the plants you intend to grow. Here are a few tips:

Hardy water lillies

Hardy water lilies can grow well at depths of 30 to 40 centimeters.

Tropical water lillies

Tropical water lilies will thrive at 30cm but can easily grow in 15 to 20cm of water as well.


Lotuses will grow well in 10 to 15 cm of water.

Emergent water plants

Emergent water plants require a constantly wet soil or at least 5 to 10 cm of water to grow well.

How often should the UV Lamp in the filter be replaced?

You should change the UV lamp or bulb in your filter at least once a year. You can do this when you perform annual pond cleaning during spring. If you see considerable amount of green water, we suggest you clean the filter and remove the layer of dirt from the lamp. If you still see green water, you might need to replace the lamp or repair the system. If you require repairs, we suggest you call a professional.

How much water flow (turnover rate) do ponds need?

The turnover rate depends on how easily water evaporates in your pond system, its size, the amount of water it has, and the amount of aquatic life it supports. Generally, in cooler climates, the turnover rate can easily be around 1.5 to 2.5 hours. However, here in Australia, it's generally accepted that turnover rates should be once an hour for ponds up to 1,000 litres, and once every two hours for ponds between 2,000 and 5,000 litres. Above 5,000 litres once every 3 hours is sufficient. The rate may change with seasons, location and fish stocking level, so we suggest checking with us to get personalised advice.

What size filter does my pond need?

It's not easy to determine what size of filter your pond will need. Here are some tips to determine the right filter size for your pond.

Calculate the pond volume

You need to understand the volume of water in your pond. You can measure the width, depth, and length of the pond to calculate the volume. The formula is average length x average width x average depth x 1000=volume litres. For a circular pond, the formula is 1/2 of diameter x ½ of diameter x 3.14 x average depth x 1000=volume in litres.

Determine the type of pond

Do you have many plants with less than 40cm of fish in 1000 litres' Average amount of plants with 80cm of fish in 1000 litres' Or few plants and more than 80cm of fish in 1000 litres' The first type will require a bigger filtration system, the second type would require a medium-sized filtration system, and the third will

Purchase more than you need

It's always a good idea to purchase more than you need. Choose something that can run 1.5 times or more the volume of water needed. That would compensate for changes in the environment and the pond. Bigger the filter, better the results.

How much should I feed my fish?

It's never a good idea to over-feed your fish as this will only add debris to your pond and strain the filtration system. Leftover food will break down into toxins that are harmful for your fish and plant life.  The ideal solution is to feed them a fixed amount once a day; alternatively, feed them small amounts twice a day. You can determine the amount by the speed at which fish eat. If they gobble the food up immediately, give them food until their pace slows down a little. If they stop consuming food within 1 minute, you can stop.