9 Reasons Why Aquaponics Fail and How To Avoid Them

Aquaponics has recently emerged as a sustainable food production system due to its efficiency and waste management. However, despite its merits and immense potential, the system is prone to failure due to some problems. So, it’s crucial to identify the reasons most aquaponics systems fail and try to avoid them to make the best out of your unit.

Here are the 9 main reasons why aquaponics fail:

  1. The aquaponics system is unbalanced.
  2. The aquaponics system has improper cycling.
  3. Using the wrong plants can cause aquaponics to fail. 
  4. Some farmers use the wrong growing media.
  5. There’s insufficient oxygen in the aquaponics system.
  6. The aquaponics system’s algae infestation is out of control.
  7. There are nutrient deficiencies within the aquaponics system.
  8. The aquaponics system has poor water quality.
  9. The pest infestation in the aquaponics system isn’t treated.

Let’s take a detailed look at these factors and the measures you can take to avoid or deal with them. Read on to learn how to establish and maintain a thriving aquaponics system.

1. The Aquaponics System Is Unbalanced

Some beginners in aquaponics aren’t aware that the system should be balanced when installing or maintaining their units. According to the Food and Agriculture Organization (FAO), a balanced aquaponics system is where the fish can produce enough waste to meet the plants’ nutrient requirements. Moreover, there should be enough plants and an effective filtration component to filter and break down fish waste.

A common reason why most aquaponics systems fail is that they’re unbalanced. In some cases, this issue occurs when the fish stocking density doesn’t match the plant volume. Hence, you’ll find that there’s a higher fish stocking density compared to a smaller plant-growing surface.

If there are too many fish in a system and fewer plants, the concentration of fish waste (and nutrients) will be higher than the plants can take. Therefore, the excessive nutrient levels will be toxic to the plants and kill them. Moreover, if the biofilter can’t convert all the waste sufficiently, the ammonia concentration in the fish tank will spike, becoming toxic to the fish.

Another problem that leads to imbalance and toxicity in an aquaponics system is the overfeeding of fish. Overfed fish will produce a lot of waste (ammonia), and you’ll also have too much uneaten food. Hence, the leftovers will decay, creating anaerobic conditions in the fish tank, as the process consumes oxygen.

Schematic diagram of a flood and drain aquaponic system

Apart from the accumulation of wastes and toxicity in the fish tank, your fish will also suffer from problems related to over-eating. So, they might suffer from diseases such as fatty liver disease or fin rot. Moreover, the excess feeds will attract other organisms to the system, including algae and molds.

How To Avoid an Unbalance Aquaponics System

So, how do you avoid an unbalanced aquaponics system?

  • Keep a low fish stocking density when starting your aquaponics unit. This will be easier to handle and won’t cause a surge in ammonia levels and consequently excessive nitrates in your system. The recommended density is 10–20 kg (22.05–44.09 lb.) per 1,000 liters (264.17 gals) of water. But this will also depend on the type and number of plants in your system.
  • Calculate the appropriate feed rate ratio to avoid overfeeding your fish. It’s a ratio that determines the daily feed portion for your fish. The ratio largely depends on the type and number of plants growing in your system. Also, the type of feed used will influence the feed rate ratio and the availability of nutrients for the plants.
  • Balance the ratio of plants and fish. The recommended ratio for green leafy plants such as kale and lettuce is 40–50 g (0.09–0.11 lb.) of fish feed per m2 of plants. For fruiting vegetables, the rate should be between 50 and 80 g (0.11 and 0.18 lb.) of feed per m2 of plants.
  • Follow a strict feeding schedule. You want to do this to avoid forgetting or overfeeding your fish. Also, allow your fish to consume all the feeds they can in the first 5 to 10 minutes. Then, remove any uneaten food to avoid decay and anaerobic conditions.
  • Choose a high-quality type of fish feed. Do this to have a balanced system and ensure the fish consume the feed. Also, the decomposed leftovers should be enough to nourish the plants. So, choose a feed type that’s nutritious, palatable, and digestible to increase the nutrient levels in the fish waste. Apart from meeting the nutritional requirements of the fish, the feed should meet the plants’ nutrient needs.

2. The Aquaponics System Has Improper Cycling

System cycling is a crucial step in establishing a new aquaponics system. The process entails building a bacterial colony that’ll facilitate the conversion of fish waste to beneficial nutrients (plant fertilizer). Hence, if cycling goes wrong, your system won’t pick up and will eventually fail.

Cycling failure results from several mistakes that many aquaponics farmers overlook. These include:

  • Using two or more ammonia sources: It’s advisable to use one source of ammonia in your system. So, if you choose to use fish as the source of this nitrogenous compound, don’t add pure ammonia or organic fertilizer to your system. Doing so will lead to excessive ammonia levels, which are toxic to the bacterial colony.
  • Failing to add enough ammonia: Some farmers only introduce ammonia in the first couple of days and fail to add more when they notice some nitrites in the system. But this will sabotage the formation of a bacterial colony as the nitrifying bacteria feed on ammonia. Hence, you should continue adding ammonia (but in smaller portions) until the bacteria start converting nitrites to nitrates.
  • Using cold water: Bacteria thrive in warm waters. Therefore, during cycling, your water temperatures should be high at around 24–30°C (75.2–86°F). But some hobbyists disregard this requirement and cycle their systems using cold water. So, this slows down the process, as the bacteria feed and multiply at a lower rate when the temperatures are low. 
  • Having poor aeration. Cycling requires a sufficient oxygen supply, as the conversion of ammonia to nitrates utilizes oxygen. Also, nitrifying bacteria thrive in aerobic conditions. Therefore, if your system isn’t well aerated, the bacterial colony won’t grow adequately, and the cycling process will drag.

That said, let’s have a look at how to cycle your system effectively:

  • Set up your aquaponics system effectively—where all the components are assembled properly.
  • Have a good source of ammonia and introduce it properly.
  • Ensure that your system is sufficiently aerated, and use warm water.
  • Monitor your system regularly by testing environmental parameters, including pH and temperature.

3. Using the Wrong Plants Can Cause Aquaponics To Fail

Although aquaponics is an ideal food production method, it’s not suitable for all plants. Hence, one of the main reasons your unit is bound to fall is introducing unsuitable plant species. But what plants are best-suited for Aquaponics?

A wide range of plants can do well in an aquaponics system, and they mostly include those crops that thrive in hydroponics. But your choice of plants will depend on several factors such as plant size, type of grow bed, and plants’ environmental requirements. Hence, larger crops like corn and some flowering plants may not do well, as they’re top-heavy and require sturdy root anchorage.

Selection of crops that do well in aquaponics systems

Before selecting the plants to grow in your system, always check their nutritional and environmental needs. And, if you want to grow non-native plants, ensure that they can also do well in your location. Moreover, it’s recommendable to go for seasonal crops, as you can plant them when the conditions are favorable.

The fish stocking density also influences what type of plants to incorporate in your Aquaponics system. Therefore, a high stocking density corresponds to plants that require large nutrient amounts, including peppers, cucumbers, and tomatoes. On the other hand, you’ll select low-nutrient plants such as lettuce, broccoli, and most herbs if your system can only accommodate a smaller fish density.

Apart from nutritional requirements, your choice of plants may also depend on the environmental needs of your fish breed. For instance, some freshwater fish such as tilapia thrive in warm waters. Therefore, if you have them in your system, it’s best to grow plants that can also do well in such an environment, including basil, cabbage, cucumbers, and pepper.

4. Some Farmers Use the Wrong Growing Media

If your aquaponics unit is a media-based system, you’ll require an inert substrate such as gravel, lava rock, or clay pebbles to grow your crops. The medium is one of the most vital components in this system type as it provides anchorage to the roots and houses the bacterial colony.

Now, some aquaponics units crumble even before the farmer has enjoyed the first harvest due to a wrong choice of growing media. So, some farmers simply go for the locally available media without considering whether it’s ideal for their systems. Additionally, an unsuitable medium will adversely affect the plants, including their appearance and taste.

So, what kind of growing media should you use in your system? It should:

  • Have a neutral pH (about 7.0)
  • Be inert (chemically inactive)
  • Retain sufficient air
  • Have good water retention but also allow it to drain to avoid water logging around the roots

Many growing media are available in the stores and can also be made at home. These include rock wool, vermiculture, river rock, hydroton, floral foam, and pine shavings. Since all these types have varying features, the best choice of a medium should also correspond to your Aquaponic unit’s size, type, and design.

However, hydroton (expanded clay pebbles) is the commonly used medium due to its attractive characteristics. The medium comprises lightweight clay balls that are pH neutral and don’t release nutrients into the water. It’s also porous, easy to clean, and reusable.

Selection of growing media commonly used in aquaponic systems

5. There’s Insufficient Oxygen in the Aquaponics System

In every aquaponics system, all the organisms (fish, plants, and bacteria) need oxygen to live. While fish and plants require oxygen for respiration, the bacteria utilize it during nitrification. Therefore, when setting up your unit, aeration must be one of the factors to consider.

The organisms in your aquaponics system will take in oxygen in its dissolved form. Moreover, different species have varying requirements for dissolved oxygen (DO). For instance, warm-water fish such as bass and catfish need approximately 5ppm (parts per million) of oxygen for survival. On the other hand, cold-water fish like trout require about 6.5 ppm.

Low DO isn’t common in small-scale aquaponics systems since they usually have smaller fish stocking densities. However, this problem is prevalent in large-scale or commercial units that stock large fish volumes. Therefore, when the DO levels are lower than 1ppm, the fish will often come to the water surface, and their health will also be at risk.

Now, apart from fish stocking density, low DO may result from the following:

  • The presence of other organisms in the system – such as snails and loaches, leads to competition for oxygen.
  • Algae blooms – deprive your Aquaponic unit of oxygen.
  • Malfunctioning air pump – fails to facilitate air circulation in the system.
  • Extremely high water temperatures – cause low absorption of oxygen.
  • Poor-quality or faulty air stones

So, to solve aeration problems, first, identify the cause of low oxygen levels. For instance, if your air pump becomes faulty, replace it with a more effective one. Also, ensure no invading organisms in the unit, including snails and algae.

However, prevention is always the best remedy. Therefore, when establishing your system, make sure that you install a functional air pump or high-quality air stones. Additionally, avoid over-feeding your fish to avoid attracting other organisms. Also, monitor the DO levels in your system regularly to identify instances where they’re lower than the optimum level.

6. The Aquaponics System’s Algae Infestation Is Out of Control

As I mentioned earlier, algae are among the organisms that invade an aquaponics system when there are many nutrients. It can result from a high fish stocking density or overfeeding your fish. Several types of algae can sneak into your system, but green algae are the most common.

Like plants, green algae have chlorophyll, a pigment that makes them green. Moreover, they have almost similar nutritional and environmental requirements. Therefore, they’ll compete with the plants for nutrients (nitrates and phosphorus) in circulation.

Though algae may seem harmless in small quantities, they grow rapidly and colonize the whole system by growing in the pipes and pumps. Hence, an algal bloom won’t only deplete the nutrients but also reduce the amount of dissolved oxygen in the system. Moreover, they alter the water’s pH levels, making it unfavorable for the fish and plants.

Now, to avoid algal bloom in your system:

  • Avoid overfeeding your fish to prevent excess nutrient production.
  • Use a dark-colored plastic or an opaque material to shade your fish tank from too much light—algae also thrive in a well-lit and aerated environment.
  • Establish an effective mechanical filter to remove algae from your unit.

7. There Are Nutrient Deficiencies Within the Aquaponics System

An aquaponics system can’t thrive if the plants have inadequate minerals. So, this occurs when the fish waste (and leftover feeds) can’t meet the nutritional requirements of the growing plants. However, not all nutrients are present in these wastes, and a farmer can use supplements to introduce them to the system.

Plant nutrient deficiency is a common problem in many aquaponics systems. Hence, it causes stunted growth and the inability to blossom, flower, or produce fruits. Consequently, this leads to poor yields or plant death.

Iron Deficiency Causes Plants To Turn Yellow

Iron is an essential micronutrient (needed in small amounts) in plants. It helps in the production of chlorophyll to make the green color in plants and enables many enzyme-powered reactions. So, when your plants lack sufficient iron, they’ll turn yellow, and the leaves will have webbed lines, leading to stunted growth.

If you start noticing these signs, it’s crucial to treat this problem to prevent crop failure. 

Therefore, supplement the iron by adding chelated iron or organic fertilizer to your unit.

Potassium Deficiency Causes Plants To Curl

Potassium is a macronutrient (needed in large amounts) that isn’t readily available in fish waste. Hence, you may also have to supplement it to meet your plants’ nutritional needs. It’s beneficial in root development as well as seed and fruit growth.

Potassium deficiency in plants causes curling and brown scorching of leaf tips and yellowing leaf veins (chlorosis). You’ll also find purple spots on the lower side of your leaves. If untreated, severe deficiency causes plant death.

So, to solve this problem, add a potassium supplement to your system. For instance, you can spray potassium chloride on your leaves or introduce a potassium solution such as potassium hydroxide, potassium sulfate, or kelp meal concentrate into your system.

Calcium Deficiency May Kill Young Plants

Calcium is another macronutrient that fish waste may not provide in your system. Therefore, like potassium, you need to supplement it into your system. But this addition can alter your system’s pH, so it’s advisable to have a balance between the two and not overdo it.

Calcium is essential in plant growth, especially flowering plants like tomatoes and pepper. Therefore, the nutrient helps strengthen the plant cell wall to produce sturdy and firm stems. It also promotes the production of flowers and fruits.

A calcium deficiency may result in the death of young leaves, flowers, and fruits. It also causes blossom end rot and deformed young leaves. Hence, treatment should start as soon as you notice these signs.

To supplement calcium in your system, add calcium hydroxide solution or spray calcium chloride foliar (on the leaves).

Phosphorous Deficiency Causes Leaves To Become Darker

Phosphorus is another macronutrient required for plant growth. Though it’s available in most fish feeds, plants may fail to absorb it effectively if the pH level in the system is unfavorable. Therefore, higher pH levels cause phosphorus precipitation, and plants can’t absorb it, leading to stunted growth.

Phosphorous deficiency is evident when the leaves appear darkened around the plant base. You may also notice a purple or reddish color in the leaves.

To supplement phosphorus in your system, add rock phosphate or chlorine-free super triple phosphate to your system. The recommended amount of phosphorus supplement in flowering plants is 20–40 ppm.

Other deficiencies can result from a lack of other nutrients, including nitrogen, magnesium, zinc, boron, and copper, just to mention a few. You can get more details on the effects of these deficiencies and how to deal with them here.

8. The Aquaponics System Has Poor Water Quality

An aquaponics system requires water, as it’s the medium where plants live and plants obtain minerals. But good water quality is essential for the organisms to survive and thrive. Hence, you must ensure that the water in your unit isn’t contaminated and has ideal conditions for fish, plants, and bacteria.

Most aquaponics units use city or municipal water with high chlorine or chloramine levels. Hence, the presence of these chemicals results in unfavorable pH levels. Therefore, it’s crucial to determine the pH level of your water (regardless of its source) and its treatment method.

If your water contains chlorine, run your system for several days to remove it. Then, test the water’s pH again to determine whether chlorine has dissipated. Although removing chlorine in a new aquaponics unit is important, topping an already established system with chlorinated water isn’t detrimental.

Now, if your water contains chloramine, you need another method to remove it or use an alternative water source. Therefore, use an activated carbon filter or a UV filter to break down the chloramine. Moreover, filtration should occur before introducing fish to the system.

Apart from pH, water temperature is another parameter that determines water quality. Different fish breeds have varying temperature requirements. Therefore, if the water doesn’t meet these conditions, the fish will experience stress and die.

It’s best to have fish species that thrive in similar environmental conditions as your locality to avoid water temperature issues. Therefore, you won’t have to incur hefty costs regulating the water temperature. But you can still have some maintenance by either heating the water or shading your fish tank from sunlight when the temperature fluctuates.

9. The Pest Infestation in the Aquaponics System Isn’t Treated

Although aquaponics systems may have fewer pest problems than other forms of agriculture, an infestation can still occur. Several pests may invade your unit, including aphids, mealybugs, caterpillars, cutworms, and beetles. Pest invasions cause stunted growth in plants, resulting in poor yields.

Since aquaponics mimics the natural ecosystem, it’s not advisable to use chemical methods to curb pest infestation. Hence, it’s recommended to consider organic mitigation approaches to maintain a sustainable and balanced system.

To control pests naturally in your system, do the following:

  • Monitor your plants regularly and remove any pests you come across (by handpicking).
  • Use a physical barrier in your units, such as a net or weed mat, to prevent pests from sneaking in.
  • Plant pest-repelling crops in your Aquaponic unit to keep pests at bay. Common pest-repellants include mint, chives, Artemisia, dill, and catnip. But carry out prior research on the best selection of these plants depending on your location.
  • Introduce beneficial insects to prevent and control pest invasions. For instance, ladybugs help in eradicating aphids by feeding on them. Also, lacewings eat several pest types, including caterpillars, aphids, thrips, mealybugs, and whitefly larvae. You can also add tachinid flies to your unit to eliminate cutworms, beetles, earwigs, squash bugs, and grasshoppers.

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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