A Look at Ammonia
It's not uncommon for reef keepers to either fixate on, or ignore ammonia levels. When in reality, it's just another parameter which provides information about the state of our reef tanks. We'll look at the different types of ammonia, their toxicity levels, and how to interpret a positive test result.
Types of Ammonia
- NH3 represents free ammonia, which is toxic in higher concentrations
- NH3-N represents the nitrogen content of NH3 without the hydrogen component
- NH4 represents ammonium, which within normal ranges, is harmless to marine life
- NH4-N represents the nitrogen content of ammonium, without hydrogen
- Total ammonia (a.k.a. TAN, or total ammonia nitrogen) is the sum of NH3 and NH4
The concentration of NH3 is greatly dependent on the potential of hydrogen (pH). Chemical reactions will quickly convert free ammonia to ammonium, and vice versa based on pH. The lower the pH, the less NH3 will be in the water. The following graph shows the percentage of NH3 to NH4 at different pH levels:
Figure 1: Percentage of Ammonia in Seawater
Toxicity Levels of Ammonia
Reef tank parameter tables often recommend keeping ammonia levels undetectable, or they might mention "typical" ocean values of less than 0.1 ppm. Plus, we've probably all read that free ammonia (NH3) is toxic to marine life, which I feel has led to some confusion about ammonia levels in our reef tanks. It's not the presence of NH3 which is a problem, but the concentration which determines toxicity. Our livestock is typically much less affected by low (but still measurable) levels of ammonia than many of us realize. So what level of NH3 is considered safe?
Both the Seachem Ammonia Alert badge and the Seneye Reef monitor categorize NH3 toxicity levels as follows:
- Safe: up to 0.02 ppm (or up to 0.25 ppm of total ammonia)
- Alert: up to 0.05 ppm (or up to 0.63 ppm of total ammonia)
- Alarm: up to 0.20 ppm (or up to 2.53 ppm of total ammonia)
- Toxic: up to 0.50 ppm (or up to 6.33 ppm of total ammonia)
Note: The above total ammonia levels were rounded to the nearest hundredth, and computed assuming 1.026 sg, 8.2 pH, and 80° F.
Scientific papers often refer to lethal concentrations which kill a specified percentage of organisms within a stated number of hours. So "96 h LC50" describes a level of lethal concentration which kills 50% of the organisms within 96 hours.
It's been reported that marine fish experience 96 h LC50 levels that range from 0.11 to 4.07 ppm of NH3 (or 1.39 to 51.50 ppm of total ammonia at: 1.026 sg, 8.2 pH, and 80° F). Note that this is a very broad range of ammonia levels, and that ammonia sensitivity varies by species of fish. Plus, this is a very high rate of mortality within a short period of time; although even sub-lethal levels of ammonia can potentially cause problems.
Fish excrete a good portion of ammonia from their bodies through their gills, via diffusion (whereby the higher level of ammonia is diffused into the lower level of your tank's water). Acute toxicity can occur when high levels of ammonia in aquarium water prevent diffusion from occurring. While this is simplified take on the subject, it helps to illustrate the point.
Based on the NH3 toxicity categories above, (at a pH of 8.2 or less) I'd consider 0.25 ppm of total ammonia to be safe, with no corrective action required. And while often well tolerated, we should typically look into the cause of total ammonia levels up to 0.5 ppm. Our goal should really be to keep ammonia to a minimum. Testing alerts us when something has changed, so we can decide if we just want to take note of it, or try to address it.
Unfortunately, I haven't found anything which tells us what levels are considered safe for inverts. So I could only guess if corals are equally affected by NH3 or not. However, I speculate that they might be less affected. But in any case, for the sake of our animals, I still feel that we should strive to keep NH3 to a minimum whenever possible.
While ammonia is an important parameter, after the cycle is fully established, most reef keepers rarely test for it because spot checks almost always confirm that ammonia is within a safe range. However, you might decide to check the level after observing visual signs of distress, experiencing a significant death in your tank, or following a particularly disruptive maintenance procedure or tank transfer.
There are a number of ammonia test kits on the market (like API, Red Sea, Salifert, and others); all of which can be used to test for ammonia. API is probably the most widely used ammonia test kit. It's affordable, easy to use, and can effectively detect low levels of total ammonia before they become a danger to our livestock. As someone who has used API's ammonia test kits for nearly two decades, I feel that it's gotten a bad rap for detecting safe levels of ammonia when there are no visible signs of livestock distress. I actually feel that it's good when a test kit can detect these elevated, but safe, levels of total ammonia.
Seachem uses a rather unique color changing disc to monitor NH3. It comes in two options: the convenient Ammonia Alert badge (shown in the pic above) which continuously monitors NH3 in your tank for up to a year, and their MultiTest Ammonia kit which uses these same discs to report NH3 (but can also test for total ammonia).
Finally, There are testers which use sensors to interpret the results (like Hanna and Seneye). While they tend to be more expensive, a digital display might be helpful for people who have problems distinguishing colors, or shades of colors.
Notes: The use of Seachem Prime can affect the color of Nessler and salicylate based kits (respectively, either changing the color of the result, or showing an inflated level of ammonia). In addition, people have questioned the claims that dechlorinators such as Seachem Prime can actually detoxify ammonia; apparently, these products have little to no effect on NH3 (or the ratio of NH3 to NH4).
Sources of Ammonia
Dead organic matter, which is broken down by heterotrophic bacteria, will result in the production of ammonia. So a substantial death or deaths can cause elevated ammonia levels. Likewise, uneaten food which is broken down by bacteria is a source of ammonia. And when fish consume food (a nitrogen source), they excrete the excess nitrogen through their gills in the form of ammonia. While we don't want to underfeed our animals, we should realize that overfeeding not only increases the ammonia production in your tank, but it adds to the organic material and inorganic nutrients in the water.
A lesser known source of ammonia is from our salt mixes. Ammonia is a common contaminate in magnesium chloride and calcium chloride. This contamination can vary by the brand (and batch) of salt. I've seen freshly mixed saltwater test as high as 0.25 ppm of total ammonia. While this might sound like a lot, your tank's biofilter should typically be able to process the ammonia fairly quickly.
- Ammonia in estuaries and effects on fish. Eddy, F.B. Environmental and Applied Biology, University of Dundee, Dundee, UK. Journal of Fish Biology (2005), 67(6), 1495-1513.
Also check out: A Guide to Cycling.