How Much Ammonia Do Fish Produce

Fishkeeping is one of the most enriching and enjoyable hobbies on earth, but it can be a bumpy road for newbies when they’re starting.

One of the most significant early challenges is establishing the nitrogen cycle in your tank.

The bioload (number of fish) in your aquarium coupled with any decaying matter such as uneaten food all contribute ammonia to an aquarium.

If the ammonia your tank inhabitants produce becomes too concentrated, it can kill them.

That’s why beginners must be able to answer the question of how much ammonia do fish produce.

So today, we’re going to cover the basics you need to know about ammonia and the nitrogen cycle so you can quickly establish a healthy ecosystem where your fish can thrive.


How Much Ammonia Do Fish Produce?

Within your aquarium, several processes are constantly in motion, and many of them create ammonia. All of these processes are closely related to the aquarium’s nitrogen cycle.

Fish create the bulk of ammonia that exists in an aquarium.

Fish metabolize the food they’re eating and excrete ammonia from the gills. Ammonia is also present in fish waste and in uneaten food that decomposes on the floor of your aquarium.

So how much ammonia do fish produce?

First, it’s important to remember that every fish is different, and the size of the fish in your tank significantly affects how much ammonia your aquarium water has.

Certain species, especially larger ones, generate more ammonia than other fish. Some of the fish that tend to produce large amounts of ammonia include:

  • Goldfish
  • Cichlids (especially larger species like Oscars, Jack Dempseys, and wolf cichlids)
  • Plecos
  • Tilapia

What Causes Ammonia

Several ongoing processes are constantly generating ammonia within your tank’s ecosystem. So let’s take a closer look at how your inhabitants and what’s in your tank affect ammonia production.


The fish inside your tank are the biggest culprits for ammonia production. Fish excrete ammonia through their gills as they metabolize their food, and it’s also found in fish waste.

Fish produce the majority of ammonia that’s present in any fish tank. Larger fish and fish that make a ton of waste create the most ammonia, like goldfish.

Dead Organic Matter

If you keep a tank with live plants, they may be another source of ammonia inside your tank. If leaves or entire plants begin to die, they release more ammonia. Likewise, if one of your tank inhabitants dies, they will create more ammonia inside your tank until you remove it.

Rotting Food

Another significant contributor to ammonia inside an aquarium is decaying food. Unfortunately, many beginner fishkeepers make the mistake of overfeeding their fish. While you may think that providing your fish with tons of food is a good way to care for them, you can do much more harm than good.

Depending on their dietary needs, it’s best to feed your fish once or twice per day and remove any uneaten food from the tank after 5-10 minutes of feeding.

Why Is Ammonia Bad?

We’ve established how much ammonia fish produce, but what does that mean for your aquarium? Ammonia is highly toxic to fish, and it can be deadly in high concentrations.

The reason why ammonia in a fish tank is such a dire predicament is that it’s toxic to your fish. Fish release ammonia through their gills and when they excrete waste.

Once a specific concentration is present in the water, your fish can no longer pass it through their gills, which causes the toxic ammonia to build up in their bodies.

Too much ammonia can cause organ failure, and ultimately, death in your fish.


Becoming a fishkeeper is a fun and rewarding hobby and an excellent way to connect yourself to the natural world. But, of course, there are some challenges to managing an aquarium, and you’ll need to learn how to manage them to provide a comfortable and safe environment for your fish.

Familiarizing yourself with the nitrogen cycle and learning how much ammonia fish produce is the first steps to keeping a beautiful and healthy fish tank.

Then, if you’re experiencing ammonia spikes in your aquarium, learn how to lower ammonia in a fish tank to provide its inhabitants with the water quality they need to thrive.

Jack Dempsey
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