Introduction to Aquaponics

What Is Aquaponics?

Aquaponics is a way of growing plants and raising fish in one connected system. The fish produce waste. Bacteria convert that waste into plant food. The plants absorb the nutrients and clean the water. The clean water goes back to the fish. Round and round it goes.

It’s part aquaculture (fish farming) and part hydroponics (growing plants in water). Put them together and you get a closed loop where both sides benefit. Fish feed the plants. Plants filter the water for the fish. Bacteria do the heavy lifting in between.

The concept isn’t new. It’s based on how natural ecosystems work. Farmers in Asia and Central America have used versions of this for centuries. Modern aquaponics just puts it into a controlled, reliable system you can run in your backyard, your garage, or even on a commercial scale.

We’ve been helping Sunshine Coast growers set up aquaponic systems for years. If you’re already into hydroponics, aquaponics is a natural next step. If you’re brand new to soilless growing, our beginner’s guide to hydroponics gives you a solid foundation first.

How the Nitrogen Cycle Works

This is the engine that makes the whole system run. If you understand these three steps, you understand aquaponics.

Step 1: Fish produce ammonia. Fish eat food and excrete waste. That waste, plus any uneaten food, breaks down into ammonia (NH3). Ammonia is toxic to fish, even in small amounts. In a normal fish tank, you’d do water changes to dilute it. In aquaponics, the bacteria handle it for you.

Step 2: Bacteria convert ammonia to nitrite. A type of bacteria called Nitrosomonas colonises the surfaces in your system (grow media, pipes, tank walls). These bacteria eat ammonia and convert it into nitrite (NO2). Nitrite is also toxic to fish, so we need one more step.

Step 3: Bacteria convert nitrite to nitrate. A second type of bacteria, Nitrobacter, converts nitrite into nitrate (NO3). Nitrate is safe for fish at moderate levels. And here’s the good part: nitrate is exactly what your plants want. They absorb it through their roots as a nitrogen source, which is one of the most important nutrients for plant growth.

So the chain goes: fish waste (ammonia) turns into nitrite, then into nitrate, then gets used by plants. The plants clean the water, and the cycle repeats. Beautiful, isn’t it?

Building up enough of these bacteria colonies takes time. That’s the “cycling” phase we’ll cover further down. Don’t rush it. The bacteria are doing the real work.

Types of Aquaponic Systems

There are three main styles. Each has its own strengths and fits different setups.

Media Bed (Flood and Drain)

This is the most popular system for home growers. You fill grow beds with a media like expanded clay balls (we stock Hydroton and similar), scoria, or gravel. Water from the fish tank floods the grow bed, soaks the plant roots and the media, then drains back to the tank.

The media serves double duty: it supports the plant roots and provides surface area for the beneficial bacteria to colonise. This means you don’t need a separate biofilter. Simple. Effective. Forgiving.

Media beds work well for a wide range of plants, from leafy greens to larger fruiting crops like tomatoes and capsicum. They’re the easiest to build and the most flexible for beginners.

NFT (Nutrient Film Technique)

NFT uses shallow channels where a thin film of nutrient-rich water flows constantly past the plant roots. Plants sit in net pots along the channel. It’s the same principle used in many hydroponic setups.

In aquaponics, NFT works best for lightweight, fast-growing plants like lettuce, herbs, and Asian greens. It’s not great for heavy fruiting plants because the roots can block the channels. NFT systems need a separate biofilter since there’s not enough surface area in the channels for adequate bacteria colonies.

NFT is more common in commercial operations where space efficiency matters and crops are uniform. For home setups, it’s doable but media beds are usually easier.

DWC Raft (Deep Water Culture)

DWC uses floating rafts (usually polystyrene sheets) that sit on top of a deep trough of water. Plants are placed in holes in the raft, and their roots dangle directly into the nutrient-rich water below.

This method is excellent for leafy greens and herbs. Commercial lettuce farms often use raft systems because they’re efficient and easy to harvest. Just lift the raft, pull the plant. Like NFT, you’ll need a separate biofilter and a solid aeration setup to keep oxygen levels high in the water.

For home growers, DWC rafts are a fun project and produce huge amounts of lettuce and herbs from a small space. But they need more attention to dissolved oxygen than media beds do.

Best Fish for Beginners in Australia

Choosing the right fish depends on your climate, whether you want to eat them, and how much effort you want to put in. Here are the top picks for Australian growers.

Barramundi

The king of Australian aquaponics. Barramundi grow fast, taste incredible, and thrive in warm water (26 to 30 degrees Celsius). On the Sunshine Coast, our climate suits them well for most of the year. They do need heated water through winter unless you have an insulated setup or a greenhouse.

Barramundi are carnivorous and grow quickly, which means they produce a lot of waste. Good for your plants. They can reach plate size (500g to 1kg) in about 12 months under the right conditions. You’ll need a decent sized tank though, at least 1,000 litres for a small school.

Silver Perch

A native Australian fish that handles a wider temperature range than barramundi (12 to 30 degrees Celsius). They’re omnivorous, which means cheaper feeding costs. Silver perch are tougher and more forgiving of beginner mistakes.

They grow slower than barra. Plan on 12 to 18 months to reach eating size. But they’re hardy, they tolerate cooler water, and they’re a great “learn on” fish. You’ll need appropriate permits in some states, so check your local regulations.

Goldfish

Don’t laugh. Goldfish are one of the most popular aquaponics fish worldwide, and for good reason. They’re cheap, tough as nails, tolerate a huge temperature range, and produce plenty of waste to feed your plants.

Obviously you won’t be eating them. But if you just want to grow herbs, lettuce, and greens without worrying about fish care, goldfish are practically bulletproof. They’re the perfect starter fish while you learn the system.

Other options for Australian growers include jade perch, Murray cod (cooler climates), and freshwater crayfish (yabbies). We can advise on which species works best for your specific setup when you come in.

Best Plants for Aquaponics

Start easy. Build confidence. Then move to the harder stuff.

Leafy Greens (Start Here)

Lettuce, spinach, kale, silverbeet, bok choy, and Asian greens all thrive in aquaponic systems. They have low nutrient demands, grow quickly, and tolerate a wide range of water conditions. If your system can grow lettuce, it’s working.

Herbs

Basil is the classic aquaponics herb. It grows like crazy and loves the nitrogen-rich water. Mint, coriander, parsley, chives, and dill all do well too. Fresh herbs on demand is one of the most satisfying parts of running an aquaponic system.

Fruiting Plants (Once Your System Matures)

After your system has been running for six months or more and the bacteria colonies are well established, you can try tomatoes, capsicum, cucumbers, strawberries, and chillies. These plants need more nutrients than leafy greens, so you’ll want a higher fish-to-plant ratio and a mature, stable system.

A common beginner mistake is jumping straight to tomatoes. Hold off. Get the system stable with leafy greens first. Then graduate to fruiting crops once you’ve got consistent readings and healthy fish.

Equipment You Need to Get Started

Here’s the basic shopping list for a home media bed system. You don’t need everything to be expensive, but don’t cheap out on the pump or the air pump.

• Fish tank. At least 500 litres for a small system. IBC (intermediate bulk container) tanks are a popular budget option. Food-grade is essential.
• Grow bed(s). Bathtub-style containers that hold your grow media. The standard ratio is about 1:1 grow bed volume to fish tank volume.
• Grow media. Expanded clay balls are the most popular. Lightweight, pH neutral, and provide excellent surface area for bacteria. Scoria (volcanic rock) works well too, and it’s cheaper.
• Water pump. Moves water from the fish tank up to the grow beds. Size it to cycle your total system volume at least once per hour. We carry a range of water and air pumps suited for aquaponics.
• Air pump and air stones. Fish need dissolved oxygen. Plants need oxygenated root zones. An air pump with air stones in the fish tank (and optionally in grow beds) keeps everything breathing.
• Plumbing fittings. PVC pipes, standpipes, bell siphons (for flood and drain), and connectors. Nothing exotic. Your local hardware store and our shop have everything.
• Water testing kit. You need to test ammonia, nitrite, nitrate, and pH regularly. An API freshwater master test kit is the standard. We also stock digital pH and EC meters.
• Fish (plus fish food). Start with fewer fish than you think you need. You can always add more once the system is balanced.
• Optional: heater. If you’re raising barramundi or other warm-water species, a submersible aquarium heater keeps temperatures stable through winter.
• Optional: shade cloth or greenhouse. Protects from extreme sun and helps regulate temperature. Pretty useful on the Sunshine Coast.

Cycling Your System (The 3 to 6 Week Startup Phase)

This is the part most beginners want to skip. Don’t. Cycling is what turns a bucket of water and some pipes into a living ecosystem.

“Cycling” means building up the colonies of beneficial bacteria (Nitrosomonas and Nitrobacter) that convert ammonia to nitrite to nitrate. Without these bacteria, ammonia builds up and kills your fish.

How to Cycle

• Fill your system with dechlorinated water. Chlorine kills bacteria, so either let tap water sit for 24 to 48 hours or use a water conditioner.
• Add an ammonia source. You can use fishless cycling (adding pure ammonia) or start with a small number of hardy fish (goldfish work well). Fishless cycling is gentler and gives you more control.
• Test daily. Use your test kit to track ammonia, nitrite, and nitrate levels. At first, ammonia will rise. Then nitrite will spike as the first bacteria colony establishes. Then nitrate will appear as the second bacteria colony kicks in.
• Wait for the pattern. Your system is cycled when ammonia and nitrite both drop to near zero, and nitrate is present and rising. This typically takes three to six weeks.
• Add fish gradually. Once cycled, add a few fish at a time. Give the bacteria a week or two to adjust to the increased load before adding more.

Patience is everything during cycling. Rushing it is the single fastest way to kill fish and get frustrated. If you want the science behind pH and testing in more detail, our pH and EC guide covers the fundamentals.

Water Parameters to Monitor

Once your system is running, regular testing keeps everything in balance. Here are the key numbers to watch.

• pH: 6.8 to 7.2. This is the sweet spot where fish are happy, bacteria work efficiently, and plants can absorb nutrients. Aquaponics pH tends to sit a bit higher than pure hydroponics (which runs 5.5 to 6.5). The bacteria and fish prefer it closer to neutral.
• Ammonia: 0 ppm. Any reading above zero means your bacteria can’t keep up, or you’re overstocked, or something is off. Small spikes happen occasionally (after adding fish, for example), but prolonged ammonia means trouble.
• Nitrite: 0 ppm. Same as ammonia. It should be zero in a cycled, balanced system. A nitrite spike usually means the second stage of bacteria hasn’t caught up to the first.
• Nitrate: 5 to 150 ppm. This is the one you want to see. Nitrate is plant food. If nitrate is climbing too high, add more plants. If it’s low, your fish-to-plant ratio might need adjusting.
• Temperature: depends on fish species. Barramundi want 26 to 30 degrees Celsius. Silver perch handle 12 to 30. Goldfish tolerate almost anything. Match your temperature to your fish choice.
• Dissolved oxygen: 5 ppm or above. Fish and plant roots both need oxygen. If your fish are gasping at the surface, boost aeration immediately. More air stones, bigger air pump, or add a splash bar where water returns to the tank.

Test at least twice a week when the system is new. Once it’s stable (after two to three months), once a week is usually enough. Always test if something looks off (sick fish, wilting plants, murky water).

Aquaponics vs Hydroponics: When to Choose Which

We get this question a lot. Both systems grow plants in water. Both produce great results. The right choice depends on what you’re after.

Choose hydroponics if: you want maximum growth speed and yield, you want precise control over nutrient ratios, you’re growing commercially and need predictability, or you don’t want the responsibility of keeping fish alive. Hydroponics is more straightforward to set up and gives faster results.

Choose aquaponics if: you like the idea of a living ecosystem, you want to grow fish and plants together, you prefer a more natural nutrient source, or you’re interested in sustainability. Once an aquaponic system is cycled and balanced, it needs less nutrient input than hydroponics because the fish are producing the fertiliser.

Key differences:

• Hydroponics uses synthetic nutrient solutions. Aquaponics uses fish waste (with occasional supplementation of iron and potassium).
• Hydroponics runs at pH 5.5 to 6.5. Aquaponics runs at pH 6.8 to 7.2 to keep the fish and bacteria happy.
• Hydroponics is easier to scale precisely. Aquaponics is a living system with more variables.
• Aquaponics doesn’t produce the salt buildup that hydroponic systems do over time.
• Aquaponics gives you protein (fish) as a second harvest. Hydroponics just gives you plants.

Many of our customers run both. A hydroponic tent indoors for controlled growing, and an aquaponic setup outdoors for herbs, greens, and fish. They’re not competing systems. They’re complementary.

Common Beginner Mistakes

We’ve helped hundreds of people set up aquaponic systems on the Sunshine Coast. Here are the mistakes we see over and over.

• Skipping the cycling phase. Adding fish before the bacteria are established is the number one killer. Be patient. Test your water. Wait for the readings to stabilise.
• Overstocking fish. More fish means more waste, which sounds good for plants. But too much waste overwhelms the bacteria and tanks your water quality. Start with fewer fish than the tank can theoretically hold.
• Overfeeding fish. Uneaten food rots and spikes ammonia. Feed only what your fish eat in about five minutes. Remove anything left over.
• Ignoring pH. Aquaponic pH naturally drifts over time (usually downward as nitrate accumulates). Check it regularly and adjust slowly using potassium hydroxide (to raise) or phosphoric acid (to lower). Never make big pH swings. Small adjustments only.
• Not enough aeration. Air pumps are cheap insurance. Fish need oxygen. Bacteria need oxygen. Plant roots need oxygen. Get an air pump that’s slightly bigger than you think you need.
• Using the wrong grow media. Limestone gravel will push your pH up. River rock may contain contaminants. Stick with expanded clay, scoria, or another proven aquaponics media.
• Trying to grow fruiting plants too early. Get your system stable with lettuce and herbs first. Tomatoes and capsicum need a mature system with a high nutrient load. Work up to them.
• No backup power plan. If your pump stops, water stops circulating, oxygen drops, and fish can die within hours in warm weather. A battery backup or at least a plan for power outages is worth thinking about.
• Placing the system in full sun without shade. On the Sunshine Coast, direct sun can heat your water to dangerous temperatures in summer. Algae also loves direct sunlight. Use shade cloth over the fish tank at minimum.

Getting Help

Aquaponics is incredibly rewarding once it’s running. Getting there takes some learning, but you don’t have to figure it all out alone.

Our team at Suncoast Hydroponics has been helping Sunshine Coast growers with aquaponic setups for years. We stock pumps, air stones, grow media, test kits, fish food, and everything else you need. More importantly, we’ve actually built and run these systems ourselves. We know what works in this climate.

Visit our aquaponics page for more on what we offer. Or get in touch with our team directly. Whether you’re planning your first backyard system or scaling up an existing one, we can point you in the right direction.

If you’re still deciding between aquaponics and hydroponics, our beginner’s guide to hydroponics covers the hydro side in detail. And for water chemistry basics, check out understanding pH and EC. Both will help you make a confident decision about which path suits you.

We’re in Kunda Park, open Monday to Friday 9am to 5pm and Saturdays 9am to noon. Come in and have a chat. We love talking about this stuff.