What Causes Ammonia In A Fish Tank (Causes, Signs & Symptoms)


A fish tank can get ammonia in any of the following ways.

  1. The leading cause of an ammonia problem is the decomposition of organic matter. The organic matter could be from aquarium plants, fish waste, overfeeding.
  2. Another cause of high ammonia levels in a fish tank could be insufficient beneficial bacteria in the aquarium.
  3. Ammonia can also result from fish metabolism and can be excreted through their gills.
  4. Too many fish or overcrowding could cause brief ammonia spikes in your aquarium as the beneficial bacteria need time to catch up to the new bioload levels created by the fish.
  5. Improper or irregular fish tank maintenance can also cause ammonia levels to rise in a fish tank as ammonia can accumulate and reach toxic levels.
  6. Lastly, high ammonia in a fish tank can occur after setting up a new aquarium. New setups have insufficient bacteria in the water column and filter media.

What Are The Signs Of Ammonia In A Fish Tank?

While you might not notice all the signs below, some common symptoms of high ammonia levels in your aquarium include:

  • Your fish might have purple, red, or bleeding gills.
  • Fish may clamp their gills closed.
  • Gills can appear darker in color.
  • You might notice red streaking on the fins or body.
  • Your fish will gasp at the surface of the tank water.
  • Fish fins might appear torn or jagged.
  • Your fish might look sluggish, lay at the bottom of the tank, or become lethargic.

However, the best way to find out if you have ammonia in your fish tank is to check the ammonia levels in your aquarium using a test kit. However, there are ways that you can test for ammonia without a kit.

What Causes Ammonia Spikes In An Aquarium?

While ammonia is always present to some extent in your aquarium, the levels can suddenly spike if you’re not careful.

Some reasons that can cause the ammonia to spike in your aquarium are improper maintenance, overstocking, overfeeding.

Another widespread problem most beginners will experience is an ammonia spike in a new tank.

This is most likely due to a lack of beneficial bacteria in the aquarium.

Many beginners add too many fish too quickly and don’t allow add enough or allow time for these bacteria to develop. This quickly leads to an issue with ammonia levels.

Final Thoughts

While it may seem like a complicated topic, keeping the ammonia in your aquarium in check is very simple.

Just follow these tips:

  • Check and monitor the ammonia levels in your fish tank
  • Perform regular maintenance & water changes
  • Don’t overstock
  • Don’t overfeed
  • Clean out any dead organic material
  • Allow your beneficial bacteria time to grow

Lastly, if you can’t get rid of ammonia in your fish tank, chemical options like aquarium ammonia removers or filter media can help remove ammonia.

For a more detailed guide check out our guide that details 10 ways you can get rid of ammonia in your fish tank.

Jack Dempsey
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