GUIDE: What Is Aquaponics

What Is Aquaponics

Aquaponics is essentially the combination of Aquaculture and Hydroponics. Both aquaculture and hydroponics have some down sides, hydroponics requires expensive nutrients to feed the plants, and also requires periodic flushing of the systems which can lead to waste disposal issues.


Re-circulating aquaculture needs to have excess nutrients removed from the system, normally this means that a percentage of the water is removed, generally on a daily basis.

This nutrient rich water then needs to be disposed of and replaced with clean fresh water. While re-circulating aquaculture and hydroponics are both very efficient methods of producing fish and vegetables, when we look at combining the two, these negative aspects are turned into positives. The positive aspects of both aquaculture and hydroponics are retained and the negative aspects no longer exist. Aquaponics can be as simple or as complex as you’d like to make it, the simple system pictured above is made from one IBC (Intermediate Bulk Container). The top was cut off and turned upside down to become a growbed for the plants. Water is pumped up from the fish tank into the growbed. The water trickles down through the media, past the roots of the plants before draining back into the fish tank.


The plants extract the water and nutrients they need to grow, cleaning the water for the fish. There are bacteria that live on the surface of the growbed media. These bacteria convert ammonia wastes from the fish into nitrates that can be used by the plants. The conversion of ammonia into nitrates is often termed “the nitrogen cycle”. This will be dealt with in more detail elsewhere on this website.

Growbeds filled with a media such as gravel or expanded clay pebbles are a common method of growing plants in an aquaponic system, but there are many different methods that can be used. In fact any method of hydroponic growing can be adapted to aquaponics. Plants can be grown in floating foam rafts that sit on the water surface. Vegetables can also be grown using NFT (Nutrient Film Technique), or through various other methods using a “run to waste” style of growing. This is done by removing a percentage of the fish water each day and watering vegetables planted in different media such as coir peat, vermiculite, perlite etc.

Many different species of fish can be grown in an aquaponic system, and your species selection will depend on a number of factors including your local government regulations. Quite high stocking densities of fish can be grown in an aquaponic system, and because of the recirculating nature of the systems very little water is used. Research has shown that an aquaponic system uses about 1/10th of the water used to grow vegetables in the ground. An aquaponic system can be incredibly productive. I’ve produced 50kg of fish, and hundreds of kilograms of vegetables within 6 months in an area about the size of your average carport, 8m x 4m.

These are the most commonly used type of aquaponic systems:

Media filled beds are the simplest form of aquaponics, they use containers filled with rock medium of expanded clay or similar. Water from a fish tank is pumped over the media filled beds, and plants grow in the rock media. This style of system can be run two different ways, with a continuous flow of water over the rocks, or by flooding and draining the grow bed, in a flood and drain or ebb and flow cycle.


Nutrient Film Technique is a commonly used hydroponic method, but is not as common in aquaponic systems. In NFT systems, nutrient rich water is pumped down small enclosed gutters, the water flowing down the gutter is only a very thin film. Plants sit in small plastic cups allowing their roots to access the water and absorb the nutrients. NFT is only really suitable for certain types of plants, generally leafy green vegetables, larger plants will have root systems that are too big and invasive, or they become too heavy for the lightweight growing gutters.


Deep Water Culture, works on the idea of floating plants on top of the water allowing the roots to hang down into the water. This can be done in a number of ways. This method is one of the more commonly practiced commercial methods. DWC can be done by floating a foam raft on top of the fish tank, however a more common method is to grow the fish in a fish tank and pump the water through a filtration system, and then into long channels where floating rafts filled with plants float on the water surface and extract the nutrients.


Which Style is Best Suited to Me?

So there are the basics of aquaponics, it really can be as simple or as complicated as you like, if you want to start off small and simple take a piece of polystyrene, cut some holes in it, stick some mint cuttings or water cress cuttings through the holes, and float it on the surface of an aquarium or pond, within no time you’ll end up with a mass of floating herbs, and you’ll have cleaner water for your fish. Through lots of experimenting over the years, and through the trials of members on the online discussion forum, the flood and drain media based system, has been found to be the most reliable and the simplest method of aquaponics, especially for beginners. It can be done very simply using a wide range of different containers. The flood and drain media bed system, also requires minimal maintenance.

We are going to concentrate on the media bed style of system, you can mix different styles of system but for the moment just straight media filled beds will do. Even with just straight media beds there are a number of different ways you can run the system.



This is a system that requires no bending, no weeding, no fertilizers, and only uses about the same power it takes to run a couple of light globes.

Importance of Fish

Fish are the power house of an aquaponics system, they provide the nutrients for the plants and if your growing edible fish, then they also provide protein for yourself. Keeping fish may be a little daunting to some, especially those without any prior experience, however you shouldn’t be discouraged. Keeping fish in an aquaponic system is more simple than keeping aquarium fish, so long as you follow simple guidelines then growing fish from fingerling size, to ready to eat fish can be extremely simple.

Choosing a fish species

There are many different species of fish that can be used in an aquaponic system, depending on your local climates and available supplies. Our local climate in Perth, Western Australia, allows us to keep Rainbow Trout through winter, then a warmer species like Barramundi during summer. There are also a few choices for year round fish that we could grow, but they often take a longer time to mature. If you live in a cooler climate you might be looking at growing Trout all year round, or perhaps another locally produced fish species. In warmer areas of Australia people generally grow Barramundi, or Jade Perch year round, in most warm areas throughout the world Tilapia is the fish of choice.


In deciding what is the best species for you to grow, you should take a few factors into account, most importantly is what you want from your system. If you don’t want to eat your fish then you probably won’t want to grow edible fish, or you may want to grow an edible fish that can live year-round in your area, so that you’re not having to harvest fish out seasonally. The second most important factor is ‘What’s available?’ You need to be able to buy fish to stock your system, even with species such as Tilapia that breed readily, you need to get your broodstock in the first place.



Here’s a list of useful aquaponic species with a few details about each:


Other Species

There are other fish species which are quite suitable for aquaponics, that might be available in your local area. In Europe many different species of carp are grown, within the United States such species as Bluegill are often available, while in Australia we also have a number of other native species like Sleepy cod which would be suitable.



Other aquatic animals that can be incorporated into an aquaponic system are fresh water mussles, fresh water prawns, and fresh water crayfish. Mussles are a filter-feeder, and do a great job of helping to clean the water, they will happily grow in flooded grow beds, or can be incorporated into fish tanks. Crustaceans make a nice addition to an aquaponic system and there are a few different species available depending on your location and water temperatures.


For those in tropical areas there’s Redclaw, a fast growing native Australian species, and for those in cooler areas there’s Yabbies or Marron.

Yabbies breed readily, given the right environment and the correct water temperature, as well as long daylight hours. They also grow fairly quickly, but they can be prone to fighting and cannibalism when stocked very densely. The Yabby is also a attractive crustacean as seen from this picture to the left.

Numbers of Fish

This can be quite a hot topic of debate amongst people who practice aquaponics. Stocking levels of fish within a system can be as high as many intensive recirculating aquaculture systems, however the higher the stocking density the higher the likelihood of things going wrong. In very heavy stocking densities you need to keep a constant eye on all water parameters to be sure that conditions are kept at the optimum.

If you lower the stocking levels of fish then you lower your levels of risk and stress. Growth rates of plants in lightly stocked systems can still be very impressive, this eight bed system was stocked with only 70 fish, thats less than 9 fish per growbed.The fish tank is 5000L and there’s a 1000L sump on the system. The fish in the system at the time of taking this photo were trout and they were around 300 – 400g. The plant growth in the eight beds was fantastic. A wide mixture of plants were grown in the beds.


Every system is different and peoples environmental conditions can vary quite a lot, but there has to be some form guideline as to what will work well for the majority of people. We recommend stocking around 20-25 fish for every 500L of growbed media in your system, this is assuming you have growbeds that are around 25-30cm deep.


Ultimately the amount of fish you can safely keep in your system depends on many factors, feed rates, water flows, oxygen levels, number of plants, pumping rates, fish species and water temperature, to name a few of the major factors. So, let’s say perhaps that you are looking at making a very simple system like the example system we have built in this manual, made from the one IBC cut into two pieces to make the growbed and fish tank. This growbed has 250L of media in it, perfect for around 10-12 fish. This is allowing for them to grow from fingerling up to a plate size of around 400-500g. If you double the growbed by adding another one the same, then you can pretty much double the amount of fish you have to 20-25 fish in the system.

This 8 bed aquaponic system with about 4000L of media and a 5000L fish tank, was running on only 70 fish when this picture was taken. That’s less than 9 fish per 500L of growbed media.

We’ve found with experimenting that you can grow a lot of plants with only a fairly lightly stocked system, and a lightly stocked system is more resilient if things happen to go wrong. Getting my fish home. You should speak to your fish supplier first, fish transporting can often depend on the size of the fish and the distance you are travelling with them, or the amount of time they will be spending in transport. Often suppliers will bag small fingerlings in clear plastic bags with oxygen added to the bag, this can allow them to be transported for long periods of time with only a slight chance of losses. Sometimes you may be required to take an esky or similar to the fish supplier, this is good so long as you take along a battery aerator with you to supply them with air for the trip.

Feeding Your Fish

We recommend that you use a quality aquaculture pellet to feed your fish, you can supplement this with alternate feeds like worms, maggots, black soldier fly larvae and plenty of other different types of alternative feed, however it’s always good to have the basis of a pellet feed there as an essential component of the fish diet. People often ask about keeping a system completely closed loop, producing all the feed you need within the system and from system rubbish and scraps. This works to a minor extent, however you must have external input into the system if you are removing nutrient from the system in the form of food to eat.

So how much do you feed your fish? Basically, as much as they want. If your system is mature then we recommend that you feed your fish as much as they want to eat within a few minutes. Any uneaten food should be removed from the system before it sinks and rots consuming oxygen from the water while increasing ammonia levels.

I Want More Fish in my System

If you want to produce more fish in your system but can’t increase the size of your growbed area then finding a way of removing solids from the system will help lower the nutrient levels. This is a fairly hotly debated area of aquaponics and really it’s up to the individual and what they want from their system. Installing some form of solids removal like a swirl separator or settling tank allows you to remove the majority of large particulates (uneaten food and fish manure) before they go into the growbed. You will however have to regularly empty these solids and dispose of them in some way, preferable into a worm farm or into your garden. Personally we prefer to leave the solids within the system, it simplifies the system while still allowing reasonable levels of fish production, and ensuring that your often expensive fish feed is put to good use, growing the plants in your system.

The following video clip will give you an idea of plant growth in an aquaponic system. Please excuse the poor quality of the images, but these are 100% real images taken daily of my system at home just outside my back door.

In any and all of the previously mentioned methods of cycling a system we recommend that people plant out their beds as quickly as possible. Personally I like to use a combination of seedlings and seeds.


Seeds germinating under the more advanced plants

You can sprinkle seeds over the top of your growbed media then plant seedlings throughout the bed. As you are digging in the seedlings to plant them, the various seeds will get buried in the media and before long they will germinate and fill your growbed.

When planting seedlings we strongly recommend washing the soil or potting mix off the roots of the seedling before planting. I know some people don’t do this, but it’s adding unnecessary contaminants to your system in the form of organic matter, sand and slow release fertilizers.

You can very simply get a bucket and put a couple of inches of water in the bottom of it, you may also like to add some seaweed extract to this or worm juice, these will aid the new seedlings in establishing well. Now simply remove the seedling from the punnet, swish it in the water and the soil should easily wash off the roots. You don’t have to be too careful to get it all off, just the majority of the soil.

When planting in your growbeds, plant everything very densely, you can plant things a lot closer together than you would in the soil because these plants with have as much water as they can want. Try and make use of areas where plant growth can expand and extend, if your system is located near a shed or wall or fence, erect something for the plants to grow up, and plant climbers like beans peas, tomatoes, cucumbers etc so that they can grow up things. Other plants you may want to let ramble, you can plant a pumpkin in one corner of your growbed, then let it spill over the side and ramble over things. Vacant unproductive land with poor or no soil is fine because the pumpkin plant gets all of its nutrient and water from the system, yet collects sunshine from where ever its long tendrils grow.

What Plants Can I Grow

I know people who have grown just about everything, from trees through to potatoes. You can pretty much grow anything, though a few things to keep in mind when deciding what you will plant. Quite a few people are growing dwarf fruit trees in half barrels as part of their system, here’s one members trees.

IBC’s and Blue Barrels for part of Ivans System


Dwarf Peach Tree


Firstly, you want to grow things that you will eat, there’s not much sense in growing lots of cabbages if you don’t really like them or eat them. You also want to be sure that you always have things growing in your system. Say perhaps you only have a simple system made from the one IBC like our sample system on this website, one growbed above the IBC fish tank. You never want to pull out all of the plants at once, otherwise there is nothing left to extract the nutrients from the system. It’s always best if you can have a broad mix in the system at any one time, mature plants, half grown plants and seedlings all at once, that way you are able to cycle through plants, removing the mature ones and planting new ones to replace them, while leaving many plants in there using up the nutrient.

To give you an idea of how plants can grow in an aquaponics system, check out some of the following pictures from members of the forum, these have all been grown in different aquaponic systems.


Backup System

Having a backup system is very handy, bordering on essential. If and when the power goes out, you want to be sure that your fish are not going to die. A well stocked system filled with fish will not last long as they consume the available dissolved oxygen within the water, so you need a way to get oxygen into the water that doesn’t rely on mains power. There are a few ways you can go about this, you can keep battery operated aerators or a generator handy for when the power goes out so that you can implement your contingency plan when things go wrong. But, generally as Murphy’s law would have it, if the power is going to go out, it will be when you are not home, so you will be unable to react to the power failure.


An AC/DC Air pump with internal battery


This means you will need to have your backup system already thought out before hand, and it will need to be automatic. There are a couple of simple ways you can do this. We like to use AC/DC aerators, these are air pumps with internal rechargeable batteries in them. Normally they run while plugged into the power, pumping air through air lines and air stones in the fish tank. When the power goes out they switch automatically over to their internal batteries and continue to pump air into the water keeping the fish alive for the life of the battery within the unit, often up to 10 hours. When the power comes back on, the internal battery is recharged. Another method used by some is to make their own back up using either water pumps or air pumps, using batteries, something like a car battery, an inverter, a trickle battery charger and a power fail switch. Essentially this does the same thing as the AC/DC air pump above, but it’s larger and in an individual components form. This type of system can be chopped and changed, you can leave out the inverter and use 12/24V DC components if they are readily available. There’s a lot more information about backup systems on the Backyard Aquaponics forum.

Pests And Deficiencies


There are a few different methods of dealing with any pests and/or diseases in your system, of course most of these require no petrochemical based sprays as these are generally very toxic to fish and also possibly the beneficial bacteria within the system. Caterpillars are easily controlled by applications of Bacillus thuringiensis, this is a natural soil borne bacteria which is available around the world under a number of different brand names. Often organically certified the spray is safe for aquaponic systems. For sap sucking insects you can use chilli and garlic sprays, these are often available commercially now a days, however they should always be used in moderation, as excess and overspray is never good. For moulds and fungus on plants you can use potassium bicarbonate sprayed onto the effected plants. Potassium bicarbonate is available under a number of different brand names around the world. It also can help a system by adding potassium, something often lacking in a system and the bicarbonate helps to keep the pH up, as most of the time pH goes down in mature systems.



If slugs are a problem, a small saucer filled with beer will attract them and they easily drown, making disposal simple and effective. Coloured sticky traps work well for thrips, aphids and whiteflies and are a good way to monitor visitors to your aquaponic system.

Dealing with deficiencies

We have found that generally supplementing for plant deficiencies is not necessary when using good quality aquaculture feed, the systems here at our display centre rarely receive any supplements, perhaps once or twice a year we might dose our systems with seaweed extract if we see some deficiencies. Deficiencies can be difficult to diagnose, thankfully there are a number of sites online which can help you diagnose particular deficiencies with images. One of the simplest ways to deal with any deficiencies is by the addition of seaweed extract. Seaweed extract is available under a number of different brand names around the world, it can also come in a powdered form or as a liquid, sometimes extracted by boiling, but often considered better if you can get liquid extracted by crushing rather than boiling as you have the advantage of getting added elements like humic acid.



Seaweed has very high levels of most micronutrients and minerals. Some other things you may want to add if the relevant deficiencies are showing in your plant growth. Chelated Iron, readily available in powdered and liquid form. Potassium bicarbonate for potassium deficiencies, so long as your pH is not high already. Be sure your pH is not high before you try and add elements to fix a micronutrient problem.



General Safety

Power supplies
Ensure that power safety is a priority at all times. Any pond pump you are using must have its power supply protected by an RCD for safety. Whenever dipping hands into the water that contains the pump, you should turn the pump o ff at the power supply first. Keep all leads well protected and out of the way of general access. Keep any electrical items like air pumps out of rain and away from water, never have an air pump sitting above your fish tank where it may get knocked into the water.


Water Risk
Be sure to have any open water protected in some way so that small children and pets cannot get into the water. Generally IBC’s are easy to protect because the IBC tank is square so it can be as simple as some heavy mesh covering your fish tank.


Top Up Water Supply
It’s a great idea to have a timer on the tap where you fill your system, there have been many stories on the forum of people putting the hose in the tank and turning on the tap to top up the system, then forgetting about it. Often this can lead to fish deaths because of the extremely low oxygen levels in the water from the tap, very large amounts of chlorinated tap water can also lead to killing off the bacteria populations which have built up in your growbeds. Tap timers are cheap and readily available and they can save a lot of heart ache.


Keep Things Safe
If you have a test kit, keep it up out of the way, this also goes for any other associated things including fish feed, keep it locked up, vermin and child safe. Not just because of the safety of the children, I’ve heard of some people that have lost their fish though small children tipping all the fish feed into the system. Just helping of course, but if you don’t spot it straight away it can lead to trouble.



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