How to Treat High Ammonia Levels

Written by casey kennedy
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Rising ammonia levels in an aquarium can be scary for any fish owner. Left untreated, high ammonia levels can lead to ammonia stress or even ammonia poisoning, which can quickly kill fish. Some signs you should watch fish for are lethargy, not eating, hovering at the bottom of the tank or gasping for air at the surface. In new tanks, high ammonia levels can happen rapidly, so learning a few ways to treat high levels can help keep your fish safe and healthy.

Skill level:
Moderately Easy


  1. 1

    Do a weekly water change. The easiest way to prevent high ammonia levels is to do a 10 to 15 per cent water change once a week. This not only helps eliminate ammonia, but weekly siphoning of old water out of the tank removes detritus (dirt) and decaying organic matter that can cause other problems within the tank.

  2. 2

    Avoid overfeeding your fish. The biggest cause of ammonia problems is overfeeding. If the ammonia level has become extremely high, stop feeding the fish for a couple of days until the level returns to zero. Most fish (except for the very young) can skip a meal or two and be fine. Removing the high ammonia level should be the main concern during this time.

  3. 3

    Keep your fish population to a minimum. When starting a new aquarium, add only a few fish at a time. Your tank will go through several changes (called a cycle) when it is first getting established. Too many fish prevent the aquarium from cycling correctly and can cause ammonia levels to spike.

  4. 4

    Remove dead fish and plants from the tank. Dead fish and plants will cause ammonia levels to rise rapidly, so remove them as soon as you notice them.

  5. 5

    Use ammonia-removal products if your fish are obviously stressed. Ammonia-removal products are considered short-term solutions and should be used only if you think your fish are in an emergency situation. These products do lower ammonia levels, but they do not correct the overall problem in the aquarium.

Tips and warnings

  • All changes made to an aquarium should be done gradually. It is easy to do too much and go from having one problem to having one that is worse. Slow and gradual steps are always best.
  • Rising ammonia levels will cause the pH level to drop. Do not attempt to raise the pH level when ammonia levels are high because this can be deadly for the fish.
  • There is no safe level of ammonia in a fish aquarium, so discovering the cause and taking immediate steps to remove or dilute it is critical.

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