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How Does A Fish Tank Get Ammonia?

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Many fish owners know that fish tanks often have ammonia and that it is bad for fish. But not everyone realizes how many different sources of ammonia there are. In this article, I will discuss how fish tanks get ammonia in the first place and what you should do to get rid of it.

Fish tanks often get ammonia via organic matter decomposition, including dead fish and plants. Other prevalent sources include food leftovers and fish waste, especially from species like oscar, plecos, clown loaches, and goldfish.

As we move forward, I will elaborate on a few other ways in which fish tanks can get ammonia. To your surprise, in some cases, fish owners themselves add it to the water deliberately.

Still curious? Feel free to check my complete guide on aquarium ammonia, where I discussed what causes ammonia, how to get rid of it, what equipment to use, and much more.

How Does A Fish Tank Get Ammonia?

Ammonia is a danger to fish. A study on the Toxic Effects of Ammonia Exposure, published in the Fisheries and Aquatic Sciences journal, exposed rockfish to varying levels of ammonia.[1]

The ammonia exposure had a negative impact on growth performance variables such as daily weight and length gain.

It can take as little as 0.05mg/L of un-ionized ammonia to damage a fish’s gills. At 2.0mg/L, the fish will die.[2] As such, you have every reason to keep ammonia out of the aquarium.

Unfortunately, aquariums cannot avoid ammonia. The substance is as commonplace in tanks as algae. But where does it come from? These are the most common sources:

1. During The Cycling Process Itself

You can introduce ammonia to an aquarium via the nitrogen cycle. Established aquariums have beneficial bacteria that turn ammonia into nitrite and then nitrate.

In the absence of that bacteria, your aquarium will struggle with frequent ammonia spikes. However, if you want to rear beneficial bacteria, you must first add ammonia to the tank.

You can use pure ammonia if you have it. But many people prefer to rely on fish food. They will add it to the tank even though the water doesn’t have fish.

Over time, it will rot, releasing ammonia. The nitrogen cycle can take as many as six weeks. 

Fortunately, the ammonia you added won’t persist.

If you succeed, the beneficial bacteria you nurtured will produce nitrates out of ammonia. Nitrates are not an issue because plants can consume the substance.

2. Dead Fish & Plants

Organic matter produces ammonia when it decays.[3] This is why experienced aquarists encourage beginners to count their fish daily. If a fish drops dead without your knowledge, it will rot, filling the water with ammonia.

Plants are just as problematic. Even though aquarium plants are expected to survive in water, they can still die. Once that happens, they will decompose, raising the ammonia concentration.

You can kill your plants and fish by failing to maintain the conditions in the aquarium. Fish require clean water with specific parameters. If you can’t give the fish what they want, the creatures will die. The plants are the same.

3. Food Leftovers & Overfeeding

You can’t starve your fish. They require at least two meals a day to survive. But you can’t expect the fish to eat every morsel you add to the tank. Some leftovers will sink to the bottom. 

These leftovers will rot and produce ammonia if you forget to remove them. Leftovers become a more significant issue when you overfeed your fish. Giving the fish more food than they can eat will increase the leftovers.

4. Fish Waste

Like most living organisms, fish produce waste, and that waste will rot unless you remove it. Overcrowding can exacerbate this issue. The more fish you have, the more waste they will produce.

If you have a small tank, the crowded conditions will encourage the ammonia concentration to spike more frequently. 

What Fish Produces The Most Ammonia?

You cannot keep ammonia out of the water because fish generate the substance. They are ammonotelic, meaning they excrete ammonia through the gills.[4]

This makes it impossible to keep the ammonia concentration low without proper cycling and strict maintenance routines. The feeding patterns matter because overfeeding can increase a fish’s ammonia production.[5]

But for many aquarists, fish waste is the biggest concern. They can’t necessarily control the amount of ammonia a fish excretes via the gills. But the same cannot be said for the waste.

If you change the water routinely and your filter is strong and reliable, you can prevent the ammonia concentration from spiking. Unfortunately, some fish species are too messy. 

One example is plecos. They generate too much waste despite their small size.[6] Oscars are another famous example.

They will destroy the balance of your aquarium unless you change the water regularly. Two other common examples are goldfish and clown loaches.

Beginners are encouraged to avoid fish of this nature because they are still inexperienced where tank maintenance is concerned. The ammonia concentration will spike faster and more frequently than they can react.

Prioritize herbivores, as they can eat flakes and pellets. Flakes and pellets are a cleaner nutritional source than live foods. They won’t make the water quite as dirty.

Does Tap Water Have Ammonia?

People don’t associate tap water with ammonia. In fact, a World Health Organization document suggested that high ammonia concentrations in tap water signified fecal pollution.[7]

They expected the substance to affect the water’s taste and smell. However, the document also admitted that a manganese-removal filter could elevate the ammonia levels in raw water.

These issues won’t concern you if you live in a modern community. However, your fish are not necessarily out of the woods. Initially, local authorities used chlorine to treat water.

But after taking note of the instability of chlorine, they introduced chloramine, a substance that combines chlorine and ammonia. Chloramine is an essential component of modern life because it makes water safe.[8]

Unfortunately, chloramine is even more dangerous to aquariums than chlorine. You can eliminate chlorine by leaving the water to stand for a day. 

Bוא אhat purification method cannot work with chloramine. Don’t expect the substance to evaporate like chlorine. Additionally, you cannot trust every water conditioner you encounter. 

Some products will only succeed in splitting the chlorine and ammonia. They will eliminate the chlorine, leaving the ammonia behind.

One solution is to use two conditioners: one that removes the chlorine and another that neutralizes the ammonia. But you are better off getting one conditioner that performs both tasks, like the Seachem Prime (link to Amazon).

Some people prefer to avoid tap water because they can’t trust it. However, well water is not necessarily better because it can add unwanted minerals and parasites to the tank. The same goes for water from a lake or pond. 

Your best option is to contact the water supplier. They will give you a detailed breakdown of every component in the water they supply to your home. Using that information, you can find a conditioner that can purify the water.

What Should I Do With High Ammonia Levels?

Ammonia levels of 0.25 ppm or higher require your attention. If it reaches 0.50 ppm, your fish will suffer and possibly die.

The first step would be to conduct a 50% water change. While this sounds like a lot, consider that your fish suffer more from ammonia intoxications.

I also suggest that you stop feeding your fish at this point. Let them fast for a couple of days. In the meanwhile, siphon the substrate and remove any leftovers you see.

You can also fight the ammonia with water conditioners. I would also recommend getting a de-chlorinator if you’re using tap water for your tank.

You can put the water conditioner while the fish are still in the tank. These products are daily safe to use.

However, it is better to remove the fish in small and overcrowded tanks for at least 15 minutes, allowing the conditioner to diffuse equally across the entire aquarium.

When cleaning your tank, make sure not to remove the filter’s media. This part contains bacteria that are highly beneficial for the nitrogen cycle. What I personally do is wash it monthly with the aquarium water.

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Fish tanks usually get ammonia when organic matter decomposes. That includes dead fish and plants, fish waste, and leftovers. The key to overcoming this issue is routine aquarium maintenance.

But you’re not alone in this fight. Beneficial bacteria, primarily found in the filter’s media, work hard to turn ammonia into nitrties via the nitrogen cycle.

There is a delicate balance in which a certain amount of ammonia is generated, followed by a certain amount that turns into nitrite (which isn’t harmful to fish).

Of course, this balance won’t hold if you don’t perform regular water changes. Usually, I recommend 15% weekly changes on tanks smaller than 10 gallons and 20% for larger ones.