Water testing series

Part 1 - Ammonia

The nitrogen cycle

The nitrogen cycle is a set of crucial processes that occur all around us in the natural world. For aquarists the key part of the nitrogen cycle we are most concerned about is the de-nitrification part. These are the processes of how dangerous nitrogenous (nitrogen-based chemicals) compounds (ammonia, nitrite & nitrate) are converted to less harmful compounds.

Nitrogen cycle diagram from Fluval Aquatics

Ammonia (NH3 – free ammonia/Un-ionized ammonia)

What is Ammonia?

Ammonia is a natural by-product released by fish and other organic sources in an aquarium (food, decaying plant matter, certain micro-organisms). The biggest cause of ammonia is usually from fish (Excreted from their gills and through their waste).

Why does it matter?

Ammonia is toxic to aquarium inhabitants! Excessive ammonia levels can burn gills and other organs, leading to extra mucus being produced to protect these tissues. This leads to fish not being able to absorb enough oxygen, and reduces how well they can transport oxygen through their blood.

Level of Ammonia ppm (Parts Per Million)


No Ammonia detected by test kits. Realistically the only safe level of ammonia


A small ammonia spike. Not ideal, but usually easily handled by a mature filter. Symptoms may begin in sensitive species of fish. Detrimental to inverts.


Most fish may show some symptoms such as struggling to breathe. May be fatal to delicate species and inverts.


Fatalities will get more common the higher the level of ammonia is. Breathing will most likely be strained in most species of fish at this point.

How can you prevent ammonia problems?

Use a water conditioner.

Chlorine (among other chemicals) kills bacteria, good and bad. Whenever starting up an aquarium or doing a water change, make sure you use a good quality water conditioner to treat your tap water to remove the problems associated with chlorine. (chlorine is also problematic to fish).

Keep up with water changes.

it’s important to do water changes frequently from the very beginning of setting an aquarium up. Not only will it help dilute waste products such as ammonia, nitrite and nitrate (among others) but it will also help keep a stable mineral content in your water. the percentage of water you need to change depends on how stocked the aquarium is as well as other factors, but as general rule anywhere from 10% to 30% weekly is sufficient.

Don’t overstock your aquarium!

The more fish you have in an aquarium will mean there is more ammonia to deal with. Upgrading your filter might help, but it will only help so far and doesn’t necessarily solve the problem. Overstocking is a particularly big problem in new aquariums. It’s important to remember the bacteria needed to break ammonia and nitrite down take a while to build up to sufficient levels.

Make sure you have adequate filtration.

Filtration is key to creating and maintaining healthy water. Not only does it remove physical debris, but, with a sufficient biological and chemical filtration, harmful chemicals can be either converted or removed.

Don’t wash your filter media in tap water!

As previously mentioned, chlorine is detrimental to filter bacteria. Washing your filter media under the tap is essentially starting back at step one. When cleaning your filter, use aquarium water instead.

Don’t overfeed.

One of the biggest culprits of excessive ammonia levels is overfeeding your fish. The more food you put into an aquarium will result in more waste being produced, not to mention leftover food that doesn’t get eaten. You can help this process by feeding less often and using foods which are more easily digested.

Upgrade your biological filtration

Biological filtration is the best way to deal with ammonia. The surface area provided by biological media acts as a home for beneficial bacteria to colonise. There are many different types of Biological filter media, and each different type will have it's benefits.

Remove organic waste.

If you are feeding ‘meat’ based treats (prawns, mussels, beef heart or even live foods such as bloodworm.) then make sure you take out any remnants before they decompose. This also goes for plant waste and vegetable treats (cucumber, courgette etc.)

Clean your tank properly.

Cleaning an aquarium is more than just water changes. Cleaning your filter regularly and properly will help eliminate a lot of stored organic waste. This goes for cleaning gravel and sand substrates as well.

How to treat an ammonia problem?

Ok, so sometimes it’s not possible to stop an ammonia spike. You might get a small ammonia spike from adding new livestock to an aquarium, changing substrate, changing filter media or even by running certain treatments (always check the instructions of any treatment beforehand for recommended ways to mitigate this). A healthy aquarium with adequate filtration will usually be able to handle this spike given time, but it is beneficial to have some tools ready if it gets out of hand.

Use biological enhancers

Adding more filter boosters/ Live filter bacteria will help re-establish biological filtration, especially in any case where the filter bacteria may have been reduced. Filter boosters are also an essential way to introduce these bacteria in new aquariums.

Use Ammonia binders

Ammonia binders are always good to have in stock just in case. Chemical filter media (zeolite for example) need to be placed into your filter to work efficiently. Whenever using chemical filter media, it’s important to understand that they act as a ‘storage’ of sorts, and will eventually be full, and need replacing.

Detoxifying ammonia

Ammonia can be detoxified by several products. Detoxifying ammonia will help stop any damage ammonia may cause by binding it to make it safe. This will NOT remove ammonia and may need to be repeated after a set time.

Ammonia (NH3) is dangerous as previously stated, but what about Ammonium (NH4+)? Ammonium is considerably less dangerous than ammonia and can be present in higher concentrations without much issue. This is why some plant fertilisers that raise Nitrogen levels will contain Ammonium (This is also because ammonium is a preferential form of nitrogen for some plants).  Ammonia and Ammonium are two sides of an equation (equilibrium) and the proportion of either is dependent on your water chemistry.

  • pH – in water that is more ‘acidic’ (below 7 pH) there will be less ammonia than in more ‘basic’ water (above 7 pH). This also works the other way round as more ammonium will be present in acidic water than basic water.
  • Temperature – the temperature of water will also determine how much ammonia is present compared to ammonium. The higher the water temperature the more ammonia will be present and the less ammonium and vice versa.

Some test kits that test for ammonia will also test for ammonium. These test kits are testing for Total Ammonia Nitrogen (TAN). Always check to see what a test kit tests for, and if you choose to use a test kit that tests for TAN keep in mind this relationship with pH and temperature when reading your results. Note: - Any raised ammonia or ammonium should be seen as something to monitor in the future and care should be taken to maintain stable pH & temperature to prevent swings.