Ammonia poisoning is caused by elevated levels of a toxic fish waste product. Ammonia is detoxified by bacteria through the aquarium nitrogen cycle. But these bacteria can be disrupted by the cycle being disrupted through heavy cleaning. Filter malfunctions, antibiotic treatments, overfeeding, and overstocking a tank can all cause ammonia in fish tank to rise.
What Causes Ammonia in Fish Tanks?
Ammonia is present in all aquatic environments, both in the natural world and in your aquarium. It comes from the decay of proteins and amino acids. It is a simple nitrogen byproduct with the chemical formula NH3.
To fish, ammonia is a poisonous compound that is eliminated from the blood through their gills. All that free ammonia would be a problem with time except it is used by plants and certain bacteria as a source of food. Plants use ammonia as a nitrogen source and make new proteins with it.
Beneficial bacteria use ammonia as food, converting it first into nitrite (NO2-). And then a second stage of bacteria consumes nitrite, converting it into nitrate (NO3-). The process is efficient and acts as the foundation for your aquarium biological filtration system.
Carnivorous fish like oscar cichlids, arowanas, and stingrays create more ammonia than herbivores like silver dollars and suckermouth catfish. A protein-rich diet means that much more ammonia needs to be excreted.
Ammonia also arises through the actions of non-beneficial bacteria. These germs feed on leftover fish food, dead plant leaves, and dead fish that haven’t been removed.
Clean water added during water changes are also a small source of fish tank ammonia. Some cities use chloramine as an antibacterial treatment for tap water instead of chlorine. Chloramine is useful because unlike chlorine it does not outgas from the water over time. Standing water won’t be infected with disease-causing bacteria.
Aquarium tap water conditioners will remove chloramine as well as chlorine. But they produce a small amount of ammonia as part of the detoxification process. Not enough to harm your fish in a clean, well cycled fish tank. But if your ammonia levels are already high it will have an impact.
Symptoms of Ammonia Poisoning in Fish
Fish with ammonia poisoning will show immediate symptoms even at low levels. There is no safe concentration of ammonia in aquarium water. If your ammonia test kit detects the compound then you should be taking corrective action.
- Lethargy: Ammonia poisoning fish causes them to stop swimming as much. They will hang in the water column or at the bottom of the tank. They may also start hiding behind a heater, plants, or other items. Even when encouraged to move, a fish with ammonia poisoning will do so slowly. Loss of appetite will also occur.
- Red, Inflamed, and Bleeding Gills: Fish ammonia burns occur on the most sensitive tissues, including the gills. They will turn bright red or even purple, if ammonia levels don’t decrease in a few days. Leaking blood will be present in advanced cases. You will also see fish gasping for oxygen and breathing faster as their gills stop working. They may also hang near the surface of the water, where oxygen levels are highest.
- Black or Red Ammonia Burns: Chemical burns also affect the skin of aquarium fish. The burns will be red or black, depending on the species of fish. Ammonia burns in goldfish tend to be black.
Constant low levels of ammonia are a source of stress in aquarium fish. Disease resistance goes down along with appetite and activity. Fish won’t breed in the presence of ammonia. Once ammonia levels start to rise it will be fatal to your fish in 1 to 7 days, depending on the species.
How to Reduce Ammonia in Fish Tank
Once you’ve identified fish ammonia poisoning you have several strategies to get your water chemistry under control.
Perform a Large Water Change
A large 50% water change is going to be your first step. I recommend this big of a water change when there are serious issues.
For regular fish tank maintenance, 20-30% is better. Aquarium fish don’t like sudden shifts in water parameters, so small and frequent changes are better. But ammonia is such a toxic compound that it’s more important to flush it out.
While you’re removing old aquarium water, dig deep into the gravel and suck up any rotting debris. Do you see a lot of leftover food and fish poop? If so then you need to rethink your feeding and maintenance routines. Lots of organic matter rotting is the primary cause of an aquarium ammonia spike.
Reduce Your Aquarium pH
Lowering the pH of your aquarium will also ease ammonia toxicity. Ammonia is more toxic as the pH goes up. The safest way to lower the pH is to use bottled additives. Follow the directions with care because the pH should be shifted over the course of several hours or days, depending on the size of the aquarium. A major shift all at once will kill your fish even faster than ammonia poisoning.
When filling your tank after the 50% water change use reverse osmosis (RO) or distilled water if you have a large source of it. These kinds of water are pH neutral (pH 7.0). They will have a slight pH lowering effect if your aquarium is hard and alkaline (pH 7.0+). A second water change with more pH neutral water will moderate it further if you don’t have a pH lowering chemical on hand.
Reduce Fish Feedings
Don’t feed as much as usual when treating ammonia poisoning. Your fish have a reduced appetite or no appetite at all right now. And any uneaten food will decay into more ammonia. They will be fine even if you don’t feed for a few days.
Perform water changes and water tests every day. And offer just a few flakes or pellets. If your fish react then offer one light feeding for the day and then no more.
Add Nitrifying Bacteria
Beneficial nitrifying bacteria live in any cycled fish tank. Sometimes they undergo natural population changes. More often they are killed when an aquarist deep cleans the filter, adds untreated tap water, or uses an antibiotic to treat a fish disease.
Nitrifying bacteria take days to weeks to re-establish themselves when killed off. During this period, ammonia levels will rise if the tank is crowded.
You don’t have to wait for the cycling process to reset on its own, however. Bottled beneficial bacteria will speed things up. These microorganisms prefer living in your filter. But will also float in the water column, eating ammonia and nitrite as they do so.
Conclusion
Ammonia poisoning fish is a major issue that will kill them if left untreated. Bleeding gills, ammonia burns, and lethargy are all symptoms. But you’ll need to use a water test kit to confirm the presence of ammonia. Large water changes, pH reduction, and adding more beneficial bacteria will detoxify ammonia in fish tanks.
FAQs
Ammonia burns sometimes act like scars and refuse to heal. The pigment changes may be permanent. But some fish will heal them and return to their original color. It all depends on the fish and how severe the ammonia burns are.
Ammonia poisoning will start to heal as soon as you reduce levels in your fish tank. Fish have natural biological pathways for excreting ammonia since it is a normal metabolic waste product. Minor cases will reverse in 3 days but it may take a week or longer for advanced cases to heal.
There is no safe ammonia level in an aquarium. The tank should be at 0 parts per million whenever you test for it. If you detect ammonia then there is a problem to address.
