Do Aquaponics Systems Need Fertilizer?

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The use of chemical fertilizers in agriculture has grown at alarming rates throughout the years. The Food and Agriculture Organization of the United Nations (FAO) projected that by 2022, the world demand for fertilizers could increase up to 200,919 tons. Although chemical fertilizer can have a beneficial impact on crop growth, its potential side-effects on personal health and the environment should not be understated. As a result, modern farming techniques like aquaponics are gaining recognition for its potential to lessen chemical use in planting. Some skeptics of aquaponics, however, are quick to point out a nutrient deficiency in crops grown through this method. Which leaves the question: do aquaponics systems need fertilizer just like soil-based plants?

The answer to this question depends on how a grower manages their aquaponic system. In the usual set-up, aquaponic crops only rely on nutrients made from fish waste to grow in a soil-less environment. So technically, the growers don’t use any kind of fertilizer. However, if the cycle becomes unbalanced due to nutrient deficiency, that’s when aquaponics practitioners may need to supplement organic fertilizers that are specially made for this planting technique. 

In this article, we are going to briefly discuss how aquaponics works and we will focus on the process of turning fish waste into nutrients. To directly address the question “does aquaponics need fertilizer?” we have also included some Organic Fertilizers in this article to help you take care of your plants if they have nutrient deficiencies.

The fish waste to fertilizer process

Aquaponics is a recirculating system of growing plants in media beds through using fish waste. Fish and other aquatic creatures such as shrimp are put in tanks where they produce excrements that are made to flow in aquaponic trays to help crops grow.

In this process, it is important to note that fish create waste in the form of ammonia, a compound that is normally toxic to both aquatic creatures and plants. Through the nitrogen cycle, this ammonia is consumed by bacteria present in the grow beds and turns them into nitrates that serve as plant fertilizer. This natural fertilizer is also present in our ecosystem. In lakes and ponds, fish waste serves as the only source of nutrient for most plants. In return, plants provide cleaner water for the fish.

Unlike chemical fertilizers that increase air pollution and mineral depletion of soil, fish waste converted into nutrients is very much organic and has no notable effect on the environment. Through the help of bacteria, even large amounts of nitrogen waste can be converted into useful nutrients.

Considerations in using fish waste as a nutrient source

To manage an aquaponic system and produce the right amount of nutrients from fish waste, the following things should be taken into account:

Fish Selection

Choosing specific fish species for your system will directly affect the amount of waste that will be converted into nutrients for your plants. In their study on managing aquaponic systems, some of the suggestions of FAO are tilapia, common carp, and silver carp because of their excellent growth rate. FAO also stresses the importance of frequently evaluating the biomass of these fish using the staggered stocking method or maintaining 3 cohorts or 3 age classes of fish in the same tank. This helps maintain a proper density ratio of fish and plants in the system which results in better nutrient production.

Fish Feeding

Feed ratio directly affects the waste production of your fish. If you want them to produce more nutrients, you have to make sure that they are consuming food that is 1% to 2% of their body weight every day. A general rule that many growers use is to provide enough food that the fish can consume in 5 minutes. In terms of the best aquaponics fish feed, choose a brand that is highly digestible and contains a lot of nutrients.

Bacteria 

Establishing a bacterial colony through system cycling is necessary if you’re new to aquaponics. To make sure that your grow beds have enough bacteria to make plant food, you should consider introducing an ammonia source to create a biofilter. In the long run, your bacteria colony will actively work on its own and would turn fish waste into nitrates naturally.

Nutrient supplementation through organic fertilizers

Despite aiming for a balanced aquaponic system, there are instances where plant deficiencies occur due to the wrong feed ratio. That’s why many traditional growers who are interested in this method are asking: does aquaponics need fertilizer aside from plant food produced by fish? Yes, definitely. According to a study made by Bittsanszky et al. in 2016,  if the plants require nutrient supplementation, organic fertilizers are most beneficial. However, you should always consult professionals in the field of aquaponics to be sure that you’re giving the right fertilizer to your crops, and they won’t negatively impact the fish. Below is a list of necessary nutrients for aquaponic plants and some common elements of fertilizers that could address a lack of them.

Nitrogen

The main reason why some plants don’t grow at their expected rate is that they lack nitrogen. If this happens, your fish are either very small to produce enough waste or the bacteria in your grow beds cannot convert ammonia into nitrates that fast. To solve this, you may use some seaweed extract in your set-up to help your plants receive more nutrients. 

Iron

Plants that experience iron deficiency exhibit signs of chlorosis or a noticeable color change. Typically, the veins of the plants remain green but their leaves turn yellow. You can use iron chelate to treat this but you have to make sure that your water’s ph level is not too high.

Phosphorus

Phosphorus deficient plants have purple-colored leaves that are heavily affected by brown spots. To add extra phosphorus to your aquaponic system, you can use bone meal fertilizer which is made of powdered animal bones.

Potassium

If your plants have cupped leaves and they easily wilt even though the temperature in your system is normal, they are most probably lacking in potassium. Your best option would be burying some banana peels in your grow beds and taking them out once they turn brown. If this doesn’t work, you can try using potassium-based organic fertilizer.

Conclusion: Do Aquaponics Systems Need Fertilizer?

Aquaponics is a farming method that utilizes fish waste as a source of plant nutrients. This is beneficial to the agricultural industry because it lessens the demand for chemical fertilizers, thus, alleviating several environmental problems such as mineral depletion of soil and air pollution. In the case of nutrient deficiencies in aquaponics systems, growers can use supplemental fertilizers that are organic and have minimal effects on their fish. This way, they can make sure that the plants are of good quality and remain chemical-free.