Choosing The Right Aquaponics Fertilizer – Do You Really Need One?

Aquaponics Fertilizer

Generally speaking, an aquaponics system is self-sustainable. While maintenance is minimum, you still have to keep an eye on it and ensure you maintain a proper balance between your fish and plants. Now, depending on the plants you have, a fertilizer is less likely to be required, especially since chemicals have been associated with numerous issues over the past few decades. In fact, this is one of the main benefits of an aquaponics system – there is no need to add any fertilizer.

But then, the necessity of fertilizer might become obvious at times. Crops tend to feed with the nutrients in fish waste. Technically, you will not need fertilizer. But the system can often become unbalanced – more fish than what plants require or the other way around. When the fish cannot produce enough fertilizer for crops, you will need to bring in some supplements – make sure they are organic and specifically formulated for aquaponics, though. Here is everything you need to know about aquaponics fertilizer.

Fish waste as a source of nutrients

There are more considerations when it comes to using fish waste as a natural fertilizer.

The fish selection is one of the main things to pay attention to. For example, a few varieties of carp and tilapia make excellent choices because they have an incredible growth rate. Evaluate the biomass of your fish on a regular basis though. After all, you need to maintain the right level of density in the system for a proper amount of nutrients.

Then, the fish feeding ratio is directly responsible for the waste production as well. You want your fish to produce more nutrients. Therefore, you need to make some changes to their diet. Stick to the food they love and up to 2% of their body weight. Simply put, give fish as much food as they require over five minutes or so, then remove the leftovers. The actual food should also be rich in nutrients, but also easy to digest.

Last, but not least, you need to come up with a healthy bacterial colony through cycling. This is mandatory and should be done before bringing the fish and plants in. An ammonia source will help in the process. You need this colony to turn fish waste into nitrates, which is what plants require to thrive. Not having enough bacteria will reduce the amount of nutrients for plants.

While pushing for a balance should be your primary goal, there will obviously be some deficiencies every now and then. In theory, you do not need an aquaponics fertilizer. But if you cannot manage this balance, you do need something. If your plants require a bit of supplementation, stick to something healthy and organic. Again, there is more research involved because while plants could thrive, fish might be hurt by the fertilizer. All in all, here are a few good options to consider.


If plants fail to grow to their regular size, chances are they do not have enough nitrogen. In this case, your fish is probably too small – you need to add more fish or wait until they grow, as they obviously need to produce more waste. On the other hand, the issue may also be in your bacterial colony – not enough bacteria will not be fast enough to turn ammonia into nitrates.

To help with the nitrogen deficiency, add a bit of seaweed extract in the system. The extract will help plants gain more nutrients from fish waste.


Are your leaves going slightly purple? Can you spot brown spots on them? You should inspect your plants on a daily basis to ensure they are disease free. If you notice any of these issues, there is a good chance your system does not have enough phosphorous. Sorting this problem out is fairly simple. Come up with some bone meal fertilizer.

Such fertilizers are made from organic elements – animal bones. They are powdered and easy to add in the system. Make sure you check the list of ingredients, and there are no chemicals in the composition, or they may affect the fish.


An iron deficiency is as harmful as any other issue, and again, there are some signs that you can pay attention to as you inspect the plants. For example, your plants will experience chlorosis. This is a visible color change – it will not happen overnight, but over days or even weeks. This is why you need to pay close attention.

While the veins stay green, leaves will turn yellow in the long run. The best aquaponics fertilizer to use in this case is iron chelate. There is one major requirement, though – make sure the pH levels in the water are not very high, or they may harm the fish.


Take a look at the leaves of your plants. Are they slightly cupped? Can you see them wilting without too much effort? Even if the temperature is right, such issues may still arise if there is a potassium deficiency in the aquaponics system. There are two different solutions.

The healthiest one involves getting a few bananas, eating them, and keeping the peels. Bury them in the actual grow bed. Once they turn brown, you can take them out. The problem should ameliorate. If it still persists, the deficiency is quite severe, so opt for a potassium fertilizer. Many of them are rich in chemicals – go for something organic.


As a short final conclusion, an aquaponics fertilizer is not necessarily a must if you manage to keep a good balance. With time, you will gain enough experience to maintain this balance. However, if you grow the system and turn it into a business, a large scale operation will be hard to keep an eye on. From this point of view, fertilizers are handy both for beginners and commercial users. Stick to organic and natural fertilizers and always double-check their impact on the fish, as you risk fixing a problem by creating another one.​

Suggested articles:
Aquaponics for Beginners – Everything You Need to Know Upfront
Aquaponics Costs – How Much To Spend For Your Organic Food
What is Aquaponics Farm? – Types, Benefits and Drawbacks
Aquaponics Water Heater – What To Know Before Getting One
What To Know Before Starting The Aquaponics Cycling Procedure
Aquaponics Tower – How Do Aquaponics Towers Work?
Aquaponics Sump Tank – Do I Need a Sump Tank For Aquaponics?

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