Why are my aquaponics fish dying? (How to stop your fish dying)

Reasons why aquaponic fish die and how to stop it

If you are reading this article because your aquaponics fish are dying, you won’t be the first to have this problem and you won’t be the last. Whilst aquaponics systems run well for the most part, they do need to be checked and monitored too. So why are your aquaponics fish dying? Let’s take a look…

Why are my aquaponics fish dying - How to stop your fish dying

Why are my aquaponics fish dying in 15 seconds…

Possibly one of the biggest reasons why aquaponics fish die is due to high levels of ammonia. High ammonia levels are toxic to fish and will kill them if you don’t get it under control. High ammonia levels can happen if your aquaponics system is new and not fully cycled. It can also happen if your fish are overfed or if the water is warmer than normal which can cause sudden spikes in the ammonia levels.


Reasons why your aquaponics fish are dying?

Before I list the reasons why your aquaponics fish are dying, it’s important to point out that you need to remove any dead fish immediately. See reason number one below and the explanation on this point.

There are a few reasons why your aquaponics fish could be dying, which include the following:

  1. High levels of ammonia.
  2. High levels of nitrites.
  3. Excessive levels of nitrates.
  4. Incorrect pH levels of the water.
  5. Low oxygen levels.
  6. Over-stocking of your aquaculture tank.
  7. Incorrect water temperature.
  8. Disease has got into your ecosystem.
  9. Your fish are dying from stress.
  10. Other toxic poisoning.
  11. Your fish are fighting each other.

Let’s take a look at each of these reasons why your fish might be dying in more detail.

1. High levels of ammonia

Ammonia is extremely toxic to fish, but it’s also a key ingredient for an aquaponics ecosystem to work too. The ammonia is what the nitrifying bacteria convert to nitrates which is the natural fertiliser for the plants.

But it’s important to keep a eye on your ammonia levels using test kits. But ammonia can be excessive for the following reasons:

  • Your aquaponics system is new and has yet to cycle: At the start of setting up your aquaponics system, before the bacteria have colonised the plant media bed, ammonia levels may be too high for fish. The lack of nitrifying bacteria will cause the build up of ammonia levels. This is the reason why it’s better to cycle your aquaponics system without fish in the beginning.
  • You could be over-feeding your fish: Over-feeding leads to excess food. This excess food decays and generates more ammonia than the bacteria can convert to nitrates.
  • Dead fish will add to ammonia levels: You may have dead and decaying fish in your tank already. With any decaying organic matter this will produce ammonia. The bacteria in your system can only convert so much ammonia. You may not have noticed a dead fish, which can lead to more deaths.

More Reading: How to lower ammonia levels in fish tank naturally aquaponics

2. High levels of nitrites

Like ammonia, if the levels of nitrites build up, this will be toxic for your fish. Nitrites are the mineral in between ammonia and nitrates. Ammonia gets converted to nitrites and then nitrites get converted to nitrates.

Just like you do with checking ammonia levels, you should also test your water for nitrite levels too.

3. Excessive levels of nitrates

Whilst the levels of nitrates can be a lot higher than both ammonia and nitrites, you still need to check these levels too. Nitrates in excess of 300 parts per million are toxic for fish and will kill them.

If your nitrate levels are too high, this could mean a couple of things. The first is that you don’t have enough plants for the number of fish you have. Alternatively, it might be you’ve got too many fish that are producing too much fish waste, which leads to more ammonia and therefore more nitrates.

You should be testing your water for nitrates too. Where the levels are too high, you need to either add more plants of remove some of your fish from the system.

4. Incorrect pH levels of the water

If the pH levels in your water are wrong this will stress your fish. If the pH is too far off what it should be this can lead to the death of some or all of your fish.

Regular testing of your water will make sure the levels of pH are correct for the type of fish you are keeping. But there’s always a bit of a trade off between the pH that fish prefer vs the pH that the plants like. However, if you can aim to keep your pH to somewhere between 6.4 to 7 this will keep your fish happy and the plants will be okay too.


5. Low oxygen levels

The level of oxygen in the water that fish require does depend on the type of fish you keep. Some fish can tolerate lower levels than others. Having said that, your water should contain enough oxygen for the type of fish you are keeping.

Low levels of oxygen will cause your fish to gulp more water in order to extract what oxygen they can. If this happens your fish will get stressed and if left unchecked they may begin to die.

To avoid this problem you need to make sure your aquaponics system has adequate aeration. This is particularly more important in the summer months, as warm water is more difficult to saturate with oxygen.

6. Over-stocking of your aquaculture tank

Over stocking your fish tank is one of the most common aquaponics mistakes that many beginner aquaponics growers make. Whilst at the beginning your fish may be small and be okay in the numbers they are when the fish are small, fish grow.

The bigger your aquaponics fish get, the more demanding they become on the water supply. Bigger fish need more oxygen and will decrease the water quality. One of the ways to keep your aquaponics ecosystem in balance is by not over-stocking your tank.

7. Incorrect water temperature

Water temperature is fish species specific, but it’s important to get the temperature right for the type of fish you choose to rear. The larger your fish tank the less susceptible it will be to fluctuations in temperature.

If you can give your fish areas of shade, but more importantly avoid large temperature swings, as this will stress your fish and can lead to them dying.

8. Disease has got into your ecosystem

It is possible that disease can get into your aquaponics ecosystem. This can happen from handling, which is advisable not to do in any case. Disease can enter your system if you use water or sample media bed from another infected aquaponics system. This is a good way to kick-start the cycling process of your newly set up aquaponics. However, always be extremely careful when transferring anything from one system to another.

Another way in which disease can enter your aquaponics ecosystem is when you introduce new fish. You are advised to quarantine your fish first before putting them into your tank.

9. Your fish are dying from stress

I’ve already mentioned a few ways in which your aquaponics fish can become stressed. This can be as a result of the wrong pH levels, high levels of ammonia, nitrites or nitrates or even the incorrect water temperature.

Fish like to school and will swim together. If they are not able to do this they can get stressed.

10. Other toxic poisoning

When you first start an aquaponics system it might be easy to forget that you’re dealing with an ecosystem that contains both plants and fish. Beginners to aquaponics may forget about how easy it is to add a non-organic food supplement for the plants or to use a pesticide on the bugs or plant diseases that is toxic to the fish.

Before adding anything to either part of your ecosystem, always check how will impact on the other part.

11. Your fish are fighting each other

Certain types of fish can be aggressive and attack other fish. This is another way in which your fish can get stressed. Be aware that whilst in some cases it’s okay to mix different fish species together, there are predatory fish too. There are also certain types of fish that can be territorial too and will fight your other fish.

Certainly at the beginning of your aquaponics journey I’d suggest sticking to one fish type in your tank. Why make life more difficult for yourself.

In an aquaponics system, do you need a water filter?

When water is transferred from your fish tank to the plant media bed it needs to be filtered. The filter is there to help keep your water clean and clear. Water filtration removes any of the solid waste from the system. However, having said that your aquaponics system should need a filter if you follow the three important rules in this article here: Do you need a water filter in an aquaponics system?

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Happy DIY aquaponics.

Why are my aquaponics fish dying? (How to stop your fish dying)

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