Ammonia is the by-product of uneaten food, dead fish, coral, invertebrates, or other organic matter as it decays in an aquarium. It is also a significant component of fish waste and is excreted through the gills or via fish poop. High levels are toxic to fish, corals and invertebrates.
What is Ammonia?
Ammonia, or NH3, is a compound made up of nitrogen and hydrogen. In humans and fish, it is a by-product of the metabolic process (i.e., digestion of food), leaving the body as liquid and solid waste. Additionally, it is also a by-product of the decomposition of uneaten food and other organic matter.
Why is it Important?
Removal of ammonia is the first step in the cycling process of a new aquarium. The presence of ammonia causes the proliferation of nitrifying bacteria. These nitrifying bacteria then convert the ammonia into nitrite. Other bacteria convert nitrite to nitrate. The remaining nitrate is then consumed by corals, removed by water changes, or adsorbed by filter media.

What is the Optimal Range?
Start of the Cycling Process: 4-6 ppm
End of the Cycling Process: 0 ppm
Cycled Aquarium/Normal Tank Operations: 0 ppm
Tools for Measuring
Most hobbyists do not regularly test for ammonia after cycling their aquarium and the level falls to 0.
Standard Test Kit:

The most common way to test ammonia is by using a standard test kit. These kits are inexpensive and straightforward to use. The most common drawback of test kits is that it can be challenging to differentiate the sample’s color accurately.
Ammonia Test Strip:

Also simple to use and inexpensive, test strips are dipped in the water for a short time and will change colors to read what the level is in an aquarium.
Digital Handheld Checker:

An easier and more accurate way to check ammonia levels. However, they are also pricier than a test kit or test strip.
What Happens if Ammonia is Not Kept in Check?
Ammonia is highly toxic to both fish and corals. The effects are almost immediate and will result in the death of both fish and coral without prompt intervention. The gills of fish will become red and inflamed (gill burn), and corals will retract and start to deteriorate almost immediately.
How to Keep Ammonia Levels in Check
In a properly cycled saltwater aquarium, ammonia is quickly converted into nitrite and then into less toxic nitrate.
Ways to prevent an ammonia spike:
- Add fish slowly and do not add too many new fish to an aquarium at one time, especially one that is not well established. The size of the fish also matters as a large, aggressive fish will produce a lot more waste and ammonia than a small fish.
- Do not overfeed. Ensure the fish in the tank can consume all the food within 2 minutes and make sure the clean-up crew can easily handle any uneaten food.
- Immediately remove any dead or dying fish and corals and any macroalgae.
What to Do if Levels Start to Increase?
If the ammonia level in the tank is too high (anything above 0.1 ppm), we recommend an immediate 25% water change. Make sure to retest after the water change is complete to make sure levels are back to normal. If levels are still very high, perform another water change the following day. Adding a source of live bacteria or an aquarium starter, such as Microbacter7, will also help reduce levels as well.
Having a reef tank ammonia test on hand is beneficial just in case the unthinkable happens. Most well-established reef tanks do not have spikes, but occasionally things can unknowingly get out of hand, and quick action is needed. Properly cycling your reef tank and taking your time stocking new fish will help prevent levels from getting too high.
Have a question? Feel free to contact us for more details regarding how to maintain your tank. If you are in the market for new tank equipment or supplies, please visit our website here: ATI North America.