Randy Holmes-Farley
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My Tank Thread
Ammonia is Our Friend
By Randy Holmes-Farley
By Randy Holmes-Farley
Yes, I know the title is provocative, and likely goes against much of what you read and hear in the reef aquarium hobby. I believe, however, that the hobby may have been harmed by the continual vilification of ammonia as something that one wants to reduce as much as possible. Products and procedures to keep driving it down may well be detrimental in many reef tanks.
This bulleted summary contains the points that I make in detail in the subsequent sections of this article along with some basic science about ammonia. If you already know you agree with certain points, it may not be needed to read those sections to get a complete story. If all you read is the summary, that may be all you need to know.
1. While ammonia is toxic at high levels, the levels needed to be lethal to a marine fish are higher than many people think. I’ve not seen any study in the literature that shows an LC50 (half of fish die) in less than 15 ppm total ammonia in seawater over 4 days or more of exposure at normal pH.
2. Sublethal toxic effects of ammonia, such as gill lesions observed by histopathology, do not seem to become significant until levels reach 5-10 ppm total ammonia at pH 8.1.
3. The toxicity of ammonia is a function of pH. At pH 8.5, toxic effects kick in at ammonia levels 2.5x lower than at pH 8.1. Likewise, at pH 7.8, it takes twice as much ammonia to be toxic as at pH 8.1. In a situation where ammonia might well reach toxic levels, such as a shipping bag, raising pH in the bag should not take place.
4. Toxic levels of ammonia are just not reached in typical operating reef aquaria. Seeing a measured value of 0.2 ppm, whether real or test error, is not a concern. It may be a benefit.
5. Commercial chemical methods to control or detoxify ammonia in marine systems at doses recommended are seemingly ineffective at impacting ammonia, despite folks thinking they were effective. If you believe that 2 ppm ammonia will kill a fish, and you add an ammonia detoxifier and it survives, you may falsely conclude it worked, as opposed to misunderstanding how toxic ammonia was.
6. Corals demonstrate a preference for obtaining the N (nitrogen) they need from ammonia over nitrate when both are available. Organisms using nitrate as an N source need to spend extra energy to convert the nitrate to ammonia before use.
7. Continually driving ammonia down in a reef tank may be making it unnecessarily difficult for corals to most easily obtain the nitrogen they need. Actions such as providing media designed for nitrifiers or adding nitrifying bacteria on a regular basis may thus be doing more harm than good.
8. Reef aquaria where N is in short supply may benefit from dosing ammonia, and that benefit may be greater than dosing nitrate. Ammonium bicarbonate is a good source of ammonia as it is inexpensive and readily available in food grade purity.
9. While measuring a detectable level of nitrate in a reef aquarium can be very useful to ensure there is some source of N available for corals, one should not assume that corals are primarily using that source since there are other sources that they may prefer to use (and actually be using).
10. “Cycling” a new reef tank with nitrifying bacteria is just one way to start a tank, and reefers should not simply accept the idea that it is the only way. It may be a fast way to add fish, but perhaps reefers should at least be aware of other options. There will be no stopping nitrifying bacteria from naturally growing in any reef system, but a system where consumption of N is the focus (corals, macroalgae, anemones etc.) as opposed to producers (fish and anything else fed outside food) may not require the addition of bacteria or the time spent waiting for them to develop.
Introduction
Ammonia (NH3) can exist in two primary forms in water. One is free ammonia, and the second is an ammonium ion (NH4+). An ammonium ion is formed when a proton in solution combines with ammonia:
NH3 + H+ <--> NH4+
Structure of ammonia __________________________________________________ Structure of ammonium
In water, H+, ammonia, and ammonium are in rapid equilibrium, and the lifetime of an individual ammonium ion is less than a hundredth of a second before it splits again to reform NH3 and H+. Water always contains protons, and the lower the water's pH, the more protons it has. In fact, a drop of one pH unit means exactly a tenfold increase in the number of protons. At lower pH, where there is a large amount of H+, the equilibrium is shifted away from ammonia and toward ammonium. This shift is actually very important in understanding its toxicity, as NH3 and NH4+ have different rates of passage across fishes' gills (ammonium is far slower).
Since the interconversion of ammonia and ammonium is so fast, on a human time scale it is often inappropriate to think of them as different species. It can be more appropriate to think of any individual ammonia molecule as spending a portion of its time as free ammonia, and a portion of its time as ammonium ion, with those relative time portions being a function of pH.
Ammonia and Ammonium as a Function of pH
The pKa of ammonium in seawater is about 9.3 (some references state 9.5, with the difference possibly relating to the different pH scales sometimes used for seawater and freshwater). That pKa means that at about pH 9.3 the water has equal concentrations of ammonium and ammonia. At pH values below this level, as is always the case in reef aquaria, ammonium predominates. Figures 1 and 2 shows a plot of the relative fractions of ammonia and ammonium as a function of pH in seawater. At pH 8.2 only about 7% of the ammonia is present as free ammonia, with 93% present as ammonium. For folks interested in testing out the effect of pH and other factors on free ammonia vs ammonium, this online calculator can be very useful.
https://www.hamzasreef.com/Contents/Calculators/FreeAmmonia.php
Figure 1. The fraction of free ammonia (NH3) and ammonium ion (NH4+) present in seawater as a function of pH.
Figure 2. The fraction of free ammonia (NH3) present in seawater as a function of pH over the range of most interest to reef aquarists.
Because many authors attribute ammonia's toxicity primarily to free ammonia, Figure 2 shows an expanded view of Figure 1 for the free ammonia concentration over the pH range of usual interest in reef aquaria. The amount of free ammonia present at pH 7.8 is about one-fourth the amount present at pH 8.5.
Reef aquarists also are often interested in pH values below those typically present in actual reef aquaria. A shipping bag containing fish, for example, often drops substantially in pH over the course of hours to days, as a result of expelled carbon dioxide. That change in pH can convert even more of the free ammonia to ammonium, and Figure 3 shows the fractions of ammonia and ammonium on a log scale, making it clear that the free ammonia continues to drop in concentration as the pH drops, even when it is already present as a very small fraction.
Figure 3. The fraction of free ammonia (NH3) and ammonium ion (NH4+) present in seawater as a function of pH. This figure shows the fraction on a log scale over a wider pH range than Figure 1.
Units of Measure of Ammonia and Ammonium
A variety of different units have been used to report ammonia concentrations. The unit "ppm NH3-N" represents the parts per million of nitrogen in the sample's free ammonia. The unit "ppm NH4+-N" represents the parts per million of nitrogen in the sample's ammonium. The unit "ppm total NH4-N" is often used to represent the sum of nitrogen in both ammonia and ammonium in the sample.
To convert ppm NH3 to ppm NH3-N, multiply by 0.82, because ammonia is 82% nitrogen by weight. To convert ppm NH4+ to ppm NH4+-N, multiply by 0.77, because ammonium is 77% nitrogen by weight. One ppm in seawater is close to one mg/L (actually 1.03 mg/L), so for most purposes in the context of ammonia in seawater, mg/L and ppm are interchangeable units.
Many chemical oceanography papers report concentrations in units of molar (M), mM or µM. One M NH3 is equivalent to one mole/L, or 17 grams per L, which equals 17,000 mg/L. One mM NH3 is equivalent to one millimole/L, or 17 milligrams per L. One uM NH3 is equivalent to one micromole/L, or 17 micrograms per L, which equals 0.017 mg/L.
I recommend that reef aquarists always think in terms of ppm total ammonia (free ammonia plus ammonium). Most test kits read total ammonia, and conversions to free ammonia are always pH dependent. Unless otherwise specified, all values in this article are in ppm total ammonia and may read as something like: “2 ppm total ammonia” or just “ammonia = 2 ppm”.
Ammonia Concentration in the Ocean
The concentration of ammonia in the ocean varies substantially, from less than 0.002 ppm to as much as 0.7 ppm total ammonia, but is usually very low in surface seawater (<0.02 ppm) because so many organisms rapidly take it up. For example, the seawater intake at the Hawaii Institute of Marine Biology (on Coconut Island, Oahu, HI; 150 feet from shore and 20 feet down) was found to have an ammonia level that ranged over 0.0025 ± 0.0021 ppm. Remote ocean surface waters are reported to have 0.006 ± 0.004 ppm total ammonia.
Sources of Ammonia in Reef Aquaria: Salt Mixes
There are a variety of sources of ammonia in reef aquaria. Minor sources include: 1) tap water (especially if it contains chloramine and is not treated with a deionizing resin) and 2) impurities in salt mixes and other additives. It has previously been shown that the total ammonia ranged from 0.008 to 0.17 ppm total ammonia in an analysis of eight brands of artificial seawater mixes. At the higher end of the scale, those levels will be detected with an ammonia test kit. These levels of ammonia may be introduced from impurities in calcium chloride and magnesium chloride, where ammonia is a well-known impurity resulting from some of the commercial manufacturing processes used (such as the Solvay process, which involves ammonia). Calcium and magnesium additives can also be a significant source of ammonia.
Sources of Ammonia in Reef Aquaria: Biological Processes
The predominant source of ammonia in marine aquaria is excretion by fish and other heterotrophs (organisms that live by consuming organic materials). Fish excrete large amounts of ammonia from their gills, and possibly smaller amounts from their urine. Heterotrophic bacteria can also be a big source of ammonia in aquaria. For example, uneaten fish food that is broken down by bacterial action will usually result in ammonia being released to the water. Many other marine organisms that are likely to be found in reef aquaria also excrete ammonia, such as crabs and shrimp. In fact, most any organism in a reef aquarium that lives by consuming food (rather than by photosynthesizing) excretes some amount of ammonia.
The reason that such organisms excrete ammonia is that they take in far more nitrogen from the organic foods that they consume than they need to build new tissues. Consequently, they must excrete nitrogen in some fashion. Ammonia is a common way to excrete nitrogen, along with urea and a few other nitrogen compounds. The chemical equation below represents the end products resulting from the metabolism of organics with a molecular formula representing typical plankton in seawater:
(CH2O)106(NH3)16(H3PO4) + 106 O2 --> 106 CO2 + 106 H2O + 3 H+ + PO4--- + 16 NH3
Mechanisms of Ammonia Excretion by Marine Fish
The mechanisms whereby marine fish excrete ammonia are different from those in freshwater fish, and aquarists must be careful not to extrapolate findings from freshwater fish to marine species without carefully considering whether it is reasonable to do so or not.
Marine fish excrete ammonia via their gills in several ways. Like in freshwater fish, free ammonia can passively diffuse out of the cells that make up the gills, and this is often the dominant pathway for excretion. This result has large implications for ammonia's toxicity to fish. Because free ammonia is passively diffusing out of cells and into the surrounding seawater, it requires a downhill gradient to proceed. If the seawater's ammonia concentration rises, this excretory mechanism does not operate effectively. It might even operate in reverse. Because it is the free ammonia concentration in the surrounding fluid that determines the ability of free ammonia to be excreted in this fashion, pH plays a substantial role in determining elevated ammonia's ability to prevent this excretory mechanism from operating. Lower pH in the surrounding seawater converts more of the ammonia to ammonium, leaving less free ammonia to back up this excretory pathway, resulting in less observed toxicity.
However, the popular scientific notion that the diffusion pathway involves simple diffusion of free ammonia through cell membranes seems no longer to be supported by recent studies utilizing modern biomolecular techniques. It is now recognized that this passive diffusion of NH3 more likely takes place through the spaces between cells, called paracellular tight junctions, and this transport phenomenon is called paracellular transport. These junctions, while usually tight enough to prevent large molecules from passing through, are leaky enough, in both marine and freshwater fish, to allow both water and ammonia to pass through.
Without going into any more detail on how freshwater and marine species differ in their free ammonia excretion (there are other important differences), a very important difference is that the paracellular junctions in marine fish are leakier than in freshwater fish, and these junctions can allow marine fish to passively excrete a substantial amount of ammonium ion. Because this pathway also involves the passive diffusion of ammonium from the blood to the surrounding fluid, the conversion of ammonia to ammonium in the ambient environment at low pH cannot completely reduce the toxicity of ammonia/ammonium in the surrounding fluid, even though it can largely do so in freshwater fish.
There are also other mechanisms whereby ammonia may be excreted from fish gills. These include an antiporter protein in the gill cell membranes that allows sodium to enter, and uses the chemical energy from that process to pump out ammonium ion. This process may not be used much at all during normal conditions, under which passive diffusion of ammonia and ammonium predominate, but may be very important when surrounding ammonia and ammonium levels rise excessively (> 1 ppm ammonia), leaving it as the only viable mechanism for ammonia excretion. Since some fish have adapted to, and survive in, such environments (certain burrow-dwelling fish, for example), this mechanism can be critical to them.
Sinks for Ammonia in Reef Aquaria: Bacterial Nitrification
Most marine aquarists are aware of the "nitrogen cycle," which begins when ammonia in the water is oxidized to nitrite by bacteria. This nitrite is then oxidized by different bacteria to nitrate:
NH4+ + 3/2 O2 --> NO2- + 2H+ + H2O
NO2- + ½ O2 --> NO3-
Many studies have examined ammonia's conversion to nitrite, and many articles have been written for professional and hobby aquarists that detail various practical aspects of the process, such as how to set up appropriate filters to facilitate this process. Many reef aquaria have no filters set up specifically for this purpose, and the bacteria that carry out this process, whether the aquarist wants them to or not, reside in coatings on most surfaces in the aquarium, including rocks, sand, glass, plastic and even on the surfaces of other organisms, such as coralline algae.
An important thing to remember, however, is that most of these bacteria reside on surfaces, so we should think of the aquarium as having (or not having) sufficient bacteria to provide nitrification, rather than the water itself as having them. This distinction is important when moving one set of organisms into a new aquarium or changing water in an aquarium. Bringing old aquarium water into a new aquarium may help to start a culture of bacteria, but will not provide much initial nitrification capacity. Bringing in rocks and sand, however, and a little old water, may be very effective in instantly providing adequate nitrification capacity.
Sinks for Ammonia in Reef Aquaria: Algae
Many organisms take up ammonia directly for use in making the proteins and other biomolecules they need to build tissues. Algae, both micro and macro, for example, readily use ammonia from the water. In cases where they are exposed to both nitrate and ammonia as nitrogen sources, many preferentially take up ammonia. When using nitrate, many of the pertinent biochemical pathways require the organism to reduce nitrate to ammonia before using it, so taking up ammonia makes sense. It has not been established in a reef aquarium setting, however, what portion of the macroalgae's nitrogen uptake is ammonia and what fraction is nitrate.
The amount of nitrogen taken up by a large macroalgal filter is substantial. A free PDF (portable document format) article in the Journal Marine Biology has some useful information with respect to the potential export abilities of algae. It gives the phosphorus and nitrogen content for nine different species of macroalgae, including many that reefkeepers maintain. For example, Caulerpa racemosa collected off Hawaii contains about 0.08% by dry weight phosphorus and 5.6% nitrogen. Harvesting a pound (454 g; dry weight) of this macroalgae from a reef aquarium would be the equivalent of removing 25.4 grams of nitrogen, which, if it were all present in 100 gallons of water as ammonia, would be equivalent to a concentration of 67 ppm total ammonia. Even if it took three months to grow to that mass, it would effectively be taking out the equivalent of 0.75 ppm total ammonia per day.
Testing for Ammonia
There are several ways to test for ammonia in seawater. These include test kits based on both salicylate and Nessler chemistry.
Nessler Test Kits
The reaction of ammonia with Nessler's reagent, K2HgI4, forms a colored precipitate of (Hg2N)I·H2O. Low levels of ammonia are yellow, higher is orange and even higher levels can be brown. The overall reaction is:
NH3 + 2[HgI4]2− + 3OH− → HgO·Hg(NH2)I + 7I− + 2H2O
One significant concern with the Nessler method is the toxicity and hazardous nature of the waste that is generated by its use (it contains mercury).
Salicylate Test Kits
Ammonia's reaction with hypochlorite forms monochloramine, which then reacts with salicylate in the presence of sodium nitro-ferricyanide to form 5-aminosalicylate. That complex is yellow to green to dark green based on the level of ammonia present. In some versions of the test, calcium and magnesium can cause interference, so be sure such a kit is designed for marine systems.
My suggestion is to always measure total ammonia. If a kit gives a choice of measuring free ammonia, don't bother. You can always use a table to convert total ammonia to free ammonia if there is a strong reason to do so. The reason to measure total ammonia is that the signal will be much larger, so the kit will be more capable of distinguishing a small reading of ammonia from no detectable ammonia.
Toxicity of Ammonia
Ammonia can be toxic to marine fish. The mechanisms of toxicity are complicated and include damage to the gills, resulting in poor gas exchange, ion regulation and blood pH regulation. Other effects include hampering oxygen delivery to tissues, disrupting metabolism and toxicity to the nervous system that causes hyperactivity, convulsions and death. Ammonia can also be toxic to many other organisms found in reef aquaria.
Toxicity can be measured and reported in many ways. One common way to measure acute toxicity is to measure how high the concentration needs to be in order to kill half of the organisms in a given time period. A commonly used time period is 96 hours (four days). Such data are called the 96 h LC50 (LC stands for Lethal Concentration, 50 meaning 50% killed). Some studies look to much longer times, such as up to 55 days to understand long term effects.
The other complication that comes with ammonia's toxicity is the relative amount of free ammonia and ammonium ion. While ammonium ion may be toxic to marine fish, it is probably less toxic than free ammonia, and toxicity data are often reported only for the concentration of free ammonia. Aquarists should recognize, however, that such data may not be appropriate if the pH used in the test, or the situation to which it will be applied, deviates significantly from normal seawater's pH (as in a shipping bag, for example, whose pH may be well below pH 8.2, and whose toxicity may actually be coming from ammonium, and not the low concentration of free ammonia). Nevertheless, many scientific articles report ammonia toxicity in ppm (or mg/L) of free ammonia. It may also be reported as just ppm NH3 (which is likely free ammonia, but can be ambiguous).
How toxic is ammonia to marine fish?
One of most interest to reef hobbyists might be this study on ocellaris clownfish.
https://link.springer.com/article/10.1007/s10499-015-9965-9#:~:text=Ammonia and nitrite can reach,2005
In this study, A. ocellaris juveniles (1.20 ± 0.34 g) were exposed to six concentrations of ammonia ranged from 0.23 to 1.63 mg/L NH3-N
The LC50- 24, LC50-48, LC50-72 and LC50-96 h were estimated to be 1.06, 0.83, 0.75 and 0.75 mg/L for NH3-N
Those values convert to total ammonia values of 19 ppm, 15 ppm, 13 ppm, and 13 ppm, respectively, at pH 8.1. Thus, half of the fish would survive 13 ppm total ammonia at pH 8.1 for 4 days. That level of toxicity is lower than many reef hobbyists assume, where many think their fish will die at 2 ppm total ammonia in a day or less.
A number of other marine fish were studied in this article with similar results, which also covers some much longer term studies:
https://nopr.niscpr.res.in/handle/123456789/47054
The authors are at the University of Antwerp, Biology Department (Belgium) and the Central Marine Fisheries Research Institute in India. Thus, it is not a hobby publication, and they have already collected a fair number of previously published experiments to summarize. As with the clownfish, it takes a lot of ammonia to kill fish.
Table 2 — Comparative toxicity of ammonia to various marine fish
| Species | Test | Result (ppm total ammonia) |
| Sea bass | 4 -Day LC50 | 40 |
| Sea bream | 4 -Day LC50 | 57 |
| Turbot | 4 -Day LC50 | 59 |
| Cat fish | 4 -Day LC50 | 45 |
| Rainbow trout | 4 -Day LC50 | 22 |
| Sea bass | 8 -Day LC50 | >22.3 |
| Sea bream | 20 -Day LC50 | 15.7 |
| Turbot | 28 -Day LC50 | 38 |
| Sea Bream | 20-Day EC50 | 15.7 |
| Turbot | 28-Day EC50 | 17-19 |
| Turbot | 55-Day EC50 | 17-21 |
| Sea Bass | 55-Day EC50 | 22 |
| LC50 = Lethal concentration for 50% of the population EC50 = Concentration reducing growth by 50% |
Concentrations of ammonia that are not acutely lethal can still cause significant problems for fish. Salmon in seawater at pH 7.8, for example, show changes in white blood cells and various blood chemicals, and were more prone to disease, when exposed to sublethal concentrations of ammonia. Consequently, aquarists should strive to keep ammonia concentrations well below lethal levels.
We have had significant additional discussion of ammonia toxicity in this thread:
https://www.reef2reef.com/threads/how-toxic-is-ammonia-really.1030601/
Corals and Ammonia
It has been shown in multiple scientific studies that corals will preferentially take up ammonia when presented with both ammonia and nitrate. This preference also makes logical sense since to use nitrate (NO3-) for any purpose, corals must remove the oxygen atoms from it, and that takes significant energy. For those interested in an extended discussion of various N uptake and use pathways in corals, this paper has many details:
https://doi.org/10.1016/j.tim.2015.03.008
from it:
“Symbiodinium [the zooxanthellae in corals] prefer uptake of ammonium over other forms of DIN [dissolved inorganic nitrogen], and ammonium may inhibit the uptake of nitrate”
Because corals prefer ammonia, they likely use it as best they can in any reef aquarium. When ammonia is low for any reason, they will take up more and more nitrate. Since accurate measurement of low levels of ammonia is not easy, ensuring there is at least a few ppm of nitrate present ensures that corals can get enough N. That does not mean that they need it or are even using it, just that N is sufficient IF they need to use it. Consequently, I recommend at least a few ppm of nitrate in any reef tank as insurance against insufficient ammonia.
Nitrification is Not Always Desirable
All reefers know from day one that ammonia can be toxic and should be reduced. However, I believe that mantra has gotten way out of hand, and many reefers are doing things that are potentially detrimental by focusing on increasing nitrification in an established reef tank. Actions such as frequently adding nitrifying bacteria, or added media whose primary purpose is to house nitrifying bacteria just seems counterproductive to me. Ammonia is almost never toxic in ordinary reef tanks, barring emergency scenarios, and pushing the ammonia <--> nitrate balance farther and farther to nitrate is making life harder for corals.
I recommend not adding nitrifying bacteria to established reef tanks unless there is some other clear reason to do so. I also recommend not adding, and in fact removing, any media whose intended function is nitrification unless the tank is very deficient in rock and sand.
Cycling a Reef Tank
The “ordinary” way to cycle a reef tank involves getting sufficient nitrifiers in place and then adding producers such as fish that add ammonia, and then later adding consumers (macroalgae, corals, etc.). As many more experienced reefers know, that is not the only way, and folks should not just accept it as best. While I am not making the claim that a reef tank at the one-year point will be better if cycled in a different way, there are other ways that obviously work.
Figure 4. A frag tank in the aquarium of Reef2Reef member FMF0331. Note the preponderance of ammonia consumers (corals) over ammonia producers (fish). Although this member used live sand in the frag tank, it may not have been necessary.
Many reefers who set up frag tanks have more consumers (corals) than producers (fish), and thus may be able to skip the standard cycle scenarios. Likewise, such readying of the aquarium can be done with other consumers such as macroalgae. A tank with sufficient macroalgae does not need nitrifiers at all, although one certainly cannot readily prevent them from growing and competing with the macroalgae for ammonia. I have, for example, put new fish in a quarantine tank where macroalgae was the way to remove accumulating ammonia, rather than any sort of sponge filter or cycled media/rock/sand.
Figure 5. A macroalgae dominated tank prepared by Reef2Reef member Elijah F. When starting his tank, he added macroalgae before any fish.
Perhaps the standard ways of cycling are the most suitable for less experienced reefers, for those who want to add fish quickly, or those who worry (perhaps correctly) that corals may not readily thrive in a brand new tank (although I’ve not really seen evidence of that when conditions are appropriate).
I really dislike the often expressed idea that “anything is possible’, because it is not, but in this case, I think reefers should be open to the idea that reef aquaria can be cycled in ways other than that which involves instant cycling with commercial bacteria.
Ammonia Concentration Guidelines
Most folks cannot readily measure the levels of ammonia that corals will readily take up, but if one can, then trying to optimize (or even stabilize) ammonia levels could be a balancing act between enough for corals and not too much for sensitive organisms. Because ammonia's toxic effects appear at levels significantly below those that are acutely lethal and because some organisms in a reef aquarium may be more sensitive than the few organisms that have been carefully studied, it is prudent to err on the side of caution when deciding what concentrations of ammonia to allow in a reef aquarium or related system.
My suggestion is to take some sort of corrective action if the total ammonia rises significantly above 0.5 ppm. That said, ammonia testing is often inaccurate at the low end of many test kits, with 0.25 ppm sometimes being the lowest a kit will actually show even when the levels are lower. In general, ammonia in an established reef tank is not going to be problematic regardless of a test result unless something unusual has happened. Such unusual situations that may cause a concerning level of ammonia are death of a large organism that is decaying in the water, a massive rockslide or sand stirring event, or a power failure. Of course, organisms in shipping bags may also experience substantial ammonia.
In previous ammonia articles, I have given info related to various commercial products that purport to detoxify ammonia in marine aquaria. Because of very extensive testing that others have performed and posted the results, I no longer have confidence that such products do what they claim, and I do not recommend using them, and certainly not relying on them. These are the very long and detailed experimental discussions that have convinced me that none of the commercial ammonia-detoxifying agents is useful:
https://www.reef2reef.com/threads/a...prime-cloram-x-rongalite-and-friends.1064206/
https://www.reef2reef.com/threads/does-prime-actually-detoxify-free-ammonia-nh3.849985/
What can one usefully do if ammonia is elevated in emergency scenarios?
Below are my suggestions for a scenario when ammonia is above 2 ppm. If ammonia is 0.5 to 2 ppm, what I would do might depend on how the tank looks overall (especially fish), why the ammonia is high, and how long I think it might go on before naturally resolving itself (e.g., ammonia from a big dead anemone that was removed may resolve rapidly while a massive rockslide with many dead and hard to remove encrusting organisms may not).
1. Stop any effort to raise pH. Such efforts might include high pH additives, or aeration with low CO2 or outside air. Do not stop aeration for oxygenation benefits, however. If a skimmer is used, just let it skim using untreated inside air.
2. Lowering pH a little might be useful, depending on the situation. If aeration is good (i.e., not a power failure or bacterial bloom situation), then adding CO2 may be a good bet. I discuss how to add CO2 here:
https://www.reefedition.com/ph-and-the-reef-aquarium/
This is a short summary of it. A drop of 0.3 pH units drops the concentration of the more toxic for of ammonia (NH3) by a factor of about 2.
Bottled or canned soda water (seltzer) can be used to instantly reduce an aquarium’s pH. Be sure to select unflavored soda water, and check its ingredients to be sure it doesn’t contain anything that should be avoided (phosphate, etc.). Many manufacturers list water and carbon dioxide as the only ingredients.
I recommend adding 6 mL of soda water per gallon of tank water to reduce pH by about 0.3 units. Add it to a high flow area away from organisms (such as in a sump). The local pH where it first is added will be very low. Going about this procedure slowly is better than proceeding too fast. If you do not have a sump, add it especially slowly. Some soda water may have more or less carbon dioxide in it than others, and the lower the aquarium’s alkalinity, the more the pH will drop. Also, the higher the pH, the less the pH will drop, because seawater’s buffering capability declines steadily as the pH drops from about 9 to 7.5.
3. Water changes can be a big help if they are big enough. Using lower pH water can be even better. In a little tank, water changes are probably the best all-around method. In a 300-gallon tank, a 50% change is a big task and may not be appropriate. A 10% water change is really not going to accomplish much in terms of ammonia toxicity if ammonia is several ppm (e.g., compare 2 ppm ammonia to 1.8 ppm ammonia after a 10% water change). Bear in mind that many salt mixes contain a small amount of ammonia (such as 0.1 ppm). That amount is not a problem, but may show on testing.
4. Removing delicate organisms to better water conditions may always be a good plan in an emergency ammonia situation. Not always easy, but always effective.
5. Bear in mind that in a shipping bag, while ammonia accumulates, so often does CO2, lowering pH and providing a protective action. Do not add tank water to high ammonia shipping water to try to match salinity because that may raise pH and increase ammonia toxicity. Rather, prepare some water at the same salinity (whatever it is) and temp, and move the fish there. Then acclimate slowly, if needed.
6. Few filter media are capable of binding ammonia from seawater. The zeolite clinoptilolite (a sodium aluminosilicate) is capable of binding ammonia from freshwater, but the sodium ions in seawater displace much of the ammonia. In fact, the ammonia binding capacity of clinoptilolite in freshwater can be regenerated by rinsing it with salty water. Consequently, its capacity to bind ammonia in seawater is very low, if any, so it is not a very useful product for marine systems. I generally don’t recommend it.
Dosing Ammonia in Low N Scenarios.
Recently, I have been suggesting that folks with low nitrate (less than a few ppm) consider dosing ammonia using ammonia bicarbonate. The results have been generally positive, and I currently recommend it over dosing nitrate.
There is a very lengthy discussion with many folk’s results in this thread:
https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087
Here is the general recipe, and I recommend the ammonia bicarbonate version unless current tank alkalinity is too high:
There are many materials that could be used for ammonia dosing, including some household ammonia solutions, but in order to give better assurance of purity, I'm electing the show directions using food grade ammonium chloride and food grade ammonium bicarbonate.
Ammonium Chloride
Ammonium chloride, NH4Cl is essentially ammonia (NH3) plus hydrochloric acid (HCl). The reason I mention that fact relates to the impact on alkalinity. Dosing NH3 followed by consumption by organisms to form tissue in a net alkalinity neutral process. I'm ignoring the fact that if it is converted into nitrate, alkalinity is lost, because if that nitrate is later used, all the alkalinity lost comes back.
However, the HCl that is effectively dosed will steadily deplete alkalinity. Adding the equivalent of 50 mg/L nitrate (0.81 meq/L; coming from NH4Cl) will have depleted 0.81 meq/l (2.3 dKH) of alkalinity. That may need to be made up for in some other fashion, such as adding more alkalinity supplement.
High quality ammonium chloride is readily available and inexpensive. Loudwolf is one brand, but there are many. Aim for food grade or ACS reagent grade. Amazon carries many Loudwolf is $7 for 4 ounces, which contains 38,000 mg of ammonium, and is equivalent to 131,000 mg of nitrate, enough to raise 100 L of aquarium water to 5 ppm nitrate about 262 times. Thus, cost is not significant.
Ammonium Bicarbonate
Ammonium bicarbonate, also known as baking ammonia, NH4 HCO3 is essentially ammonia (NH3) plus CO2 and water.
As mentioned above, dosing NH3 followed by consumption by organisms to form tissue in a net alkalinity neutral process. The CO2 and water also do not impact alkalinity. Thus, ammonium bicarbonate is a net alkalinity neutral way to dose ammonia.
High quality ammonium bicarbonate is also available from Amazon as baking ammonia. It is readily available and inexpensive. One brand sells 11 ounces for $15, so it's cost is similar to the Loudwolf ammonium chloride per unit of ammonia added (one needs to use more of the ammonium bicarbonate than the ammonium chloride, evening out the cost).
Stock Solution
Using either of these materials, we will make a stock solution for dosing. Keep it closed, as it will smell of ammonia and slowly loses ammonia to the air. Ammonium bicarbonate will have a higher pH, smell more, and lose ammonia to the air faster.
13.5 grams of ammonium chloride (about 3 - 4.6 teaspoons, varies by brand) in 1 L RO/DI water.
OR
20 grams of ammonium bicarbonate (about 4 and 3/4 teaspoons) in 1 L RO/DI water.
Both solutions contain approximately 4300 mg/L (4.3 mg/mL) ammonia, equivalent to 15,700 mg/l nitrate.
Dosing
Don't be overly afraid of dosing ammonia due to toxicity, but one cannot dose substantial amounts all at once. IMO, it is safe to add 0.1 ppm ammonia (equivalent to 0.36 ppm nitrate) at once to any reef tank, and one can likely add more, if it mixes in well. Don't dose it right onto a fish, but dosing 2-3x that amount at once is also likely OK. Of course, using a dosing pump to spread out the dosing is fine and may be preferable, but be sure to guard against dosing pumps out of control (e.g., stuck on). Stock solutions can be increased or decreased in potency to match pumping needs. The ammonia could also be put into an ato since exact daily dosing is not required.
To add 0.1 mg/L ammonia to an aquarium, you would need to add 2.3 mL of either stock solution to a 100 L (26 gallon) aquarium. You may need to add this amount multiple times per day to dose enough.
I'd add it to a sump, if possible, to dilute it well before it gets to the main tank. Most folks dosing ammonia wouldn't also be using media intended to push the nitrogen cycle in various ways, but if you do, dose downstream of that media.
Of course, if anything seems to react badly the first time or two that you dose, stop dosing, double check the amounts, and perhaps come back to this thread for further discussion of what might be happening.
One can use this calculator for dosing these stock solutions. Use the entry for ammonia from ammonium nitrate when using the ammonium bicarbonate. For ammonium chloride, use it the same, but dose 0.7 times the amount it says to add to the aquarium.
James' Planted Tank - Dosing Calculator
Summary
Ammonia can be toxic to marine fish and other organisms in a reef aquarium. While routine ammonia measurement is not required in established reef aquaria, it can be important when fish are in temporary quarters, such as shipping bags, hospital tanks and quarantine tanks. Most aquarists associate ammonia with new aquarium "cycling," and in that situation it is important to wait for ammonia to decrease to low levels (<0.5 ppm or so) before adding organisms (much more important than waiting for nitrite to decrease, for example). Ammonia can also be important during tank crashes. In all of these situations, I recommend striving to keep ammonia below 0.25 ppm total NH4-N.
That said, ammonia is also an important source of nitrogen for many organisms such as corals. I do not recommend trying to drive ammonia as low as possible. This last suggestion may be new to many reef hobbyists, and if nothing else is taken away from this article, that may be the most important.
Remember, ammonia can be your friend!
Happy Reefing!
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