Ammonia Control in Aquaculture: What you need to know
Every fish farmer knows about ammonia. It’s a constant battle, especially in warmer months, to keep levels low and your fish and shrimp healthy.
But what is ammonia? Why does it cause problems in aquatic life? Outside of testing, what are the best steps you can take to eliminate ammonia?
Here, we outline the answers to those questions.
Ammonia, as a colorless chemical compound, is composed of nitrogen and hydrogen that is highly irritating and poisonous with a distinctive strong pungent smell in its natural form. It is a common nitrogenous waste among aquatic organisms yet nutritional to terrestrial life that serves as food and fertilizer.
Ammonia, when present in water, can be measured as Total Ammonia Nitrogen (TAN). TAN is both ionized ammonia (NH4+) and unionized ammonia (NH3) existing simultaneously.
NH3 is what we typically know as ammonia. When it dissolves with water, it forms ammonium ions also known as NH4+. This unionized form is less able to pass through the gill membranes than the ionized form (NH3), making it less harmful to fish.
How Ammonia Accumulation Happens in Ponds
Ammonia in aquaculture ponds comes from several places.
First, it can be produced through the normal metabolic processes of fish in digesting feed, particularly those containing proteins. When this protein component is broken down by the fish for energy, ammonia often becomes a by-product. It is then excreted through the gill membranes, with a small amount excreted in the urine.
Second, it can come from the breakdown of waste accumulating on the pond bottom (“the sludge”). A few of the sources of that waste are:
Uneaten fish feed (from overfeeding)
Fish farm waste / fecal solids
Dead algae (particularly in late fall to winter or during algal blooms
As these compounds break-down, they often release ammonia as a by-product.
Because of the effects of temperature on ammonia levels, it is often believed that ammonia management is less important during the winter months. In practice, however, the concentration tends to be higher in the winter because algae levels (a typical tool for ammonia management – see link to learn more) are low compared to summer.
Full-season management is a must, no matter the time of year.
The Negative Effects of Ammonia on Shrimp & Fish
Safe ammonia levels vary greatly based on the water temperature, night-to-day temperature shifts of the climate, pH, and fish/shrimp species cultured. Consult with your local technical experts and/or veterinarians for proper guidance.
However, even small amounts can be harmful if fish/shrimp are chronically exposed. The presence of 0.05mg per liter of un-ionized ammonia can be harmful to fish and can adversely affect their growth. As it reaches this level, it irritates the fish, causing increased health deterioration and stress. In turn, they become susceptible to bacterial infection and their resistance to disease would decrease.
Worse, concentrations greater than 2.0mg per liter of un-ionized ammonia can be deadly to fish, although many fish ponds do experience periods of free ammonia above 4-5 mg. Studies show that ammonia toxicity is among the reasons for a low fish hatch.
The amount of ionized ammonia – an indicator of the toxicity of the ammonia – requires a bit of calculation, as it’s a function of temperature, pH, and TAN. We’d recommend a free online ammonia calculator, like this one from Iowa State University.
This more toxic form is more present with higher pH and temperature. The ratio of NH3to NH4 increases ten-folds for each unit rise in pH alone. And as temperature increases by an additional 50⁰F, NH3-to-NH4 ratio increases twice as much.
Ammonia Management: What you can do to prevent ammonia accumulation
Surprisingly simple management activities have been shown to help keep ammonia levels checked.
Here are some of those aquaculture tips to protect your fish and shrimp.
Testing kits. Good water quality is the key to successful aquaculture. Low-cost self-service test kits can be used to monitor ammonia, temperature, and pH levels on a regular basis. By tracking levels, you can get ahead of spikes in ammonia, treating the underlying issues before they can drive ammonia to toxic levels. On a large scale, , submersible in-pond products can be a more practical choice. This equipment continuously monitors a variety of water parameters including ammonia, and provides an accurate and more detailed record to serve as an early warning system.
Maintaining the acidity in water can also help reduce the ammonia build-up in water because toxic ammonia or un-ionized one usually does not thrive at a lower pH level. Therefore, maintaining the acidity level can be a helpful way to maintain a tolerable ammonia level in fish ponds. The addition of a liming agent can work to correct the pH values.
Aeration and Flushing with freshwater. The un-ionized ammonia is in the form of dissolved gas. Increasing pond aeration or the process of removing dissolved gases is another way of decreasing ammonia concentration in a fish pond. In a small scale pond, aerating will remove the dissolved toxic ammonia through diffusion from water into the air. Flushing the pond with fresh water can also dilute the concentration of ammonia which in turn could lessen water toxicity. Both ways (aeration and flushing with freshwater) of lessening the toxic concentration of ammonia can only be practical on a small scale than in larger aquaculture operations.
Aquatic Plants and Organisms. Aquatic plants play a vital role in aquaculture water treatment. Algae and other aquatic plants take and consume a huge amount of ammonia in a fish pond. Aside from producing oxygen, plants such as yucca reduce harmful and toxic substances. Algae, in contrast, uses ammonia to harness energy from sunlight. It acts like a sponge that absorbs ammonia in its process of photosynthesis. Thus, both produce a positive effect in the maintenance of the tolerable presence of ammonia in a fish pond. Research suggests that the presence of plants and other aquatic organisms such as algae acts as a natural process in the loss or transformation of ammonia. Oxygenating plant species are always a good recommendation unless for commercial scales, air pumps would mostly do the trick. Oxygen levels can be controlled by means of stocking fish at a reasonable density, this also aids in the calculated proportion of feed consumed by fish to help eliminate excess feed.
Reducing/Increasing Pond Depth. In shallow ponds, algae would usually thrive because of ample availability of light. Because of the high availability of light, algal growth will increase. This, in effect, will remove the ammonia more effectively. On the contrary, the increased depth of the pond is also another way to reduce or preserve the essential level of ammonia in ponds. Deeper ponds contain more water than in shallow ponds. They should have lower toxic ammonia concentrations because there is more water to dilute the ammonia excreted by fish.
Reduction of feeding. Protein from the feed of fish is the major cause of ammonia build-up in water. In the process of metabolizing protein, ammonia is necessarily produced. When ammonia is found present, reduction or elimination of feeding is done. In winter, feeding is only done at higher temperatures of around 50 F. Contrary to what most people believe, ammonia is low in summer due to the intense photosynthetic activity of algae in removing ammonia. Unmonitored feeding will most likely impose ammonia concentration in months without algal interventions. When feeding is regulated, fish are not likely to eat feed due to ammonia stress and the feed will only make the situation worse upon accumulation. In this case, changing 25 to 50% of total water volume is recommended to remove some for the ammonia in smaller ponds/tanks.
Hence, controlling the feeding rate can reduce the concentration of ammonia. A managed conservative manipulation of the feeding rate can also reduce the risks brought by excessive and prolonged exposure to ammonia.
Invest in beneficial bacteria and probiotics. There are plenty of benefits to the use of quality probiotics products in aquaculture. Studies show that the addition of booster probiotics can address the problem of too much accumulation of toxic ammonia in water. Many of these probiotics are preventative products – working by reducing the accumulation of excess organic waste and fish urine. In fact, if added to a high-ammonia pond, they will drive ammonia upwards as their bio-remediation process occurs.
While nitrifying bacteria have been tested in labs, their efficacy in practice is unproven and products are often unstable. As a result, these should be used proactively to ensure a healthy water environment.
The long-term success of the aquaculture industry rests careful, scientific management practices to produce high-quality yields. In addition, farms should arm themselves with a full toolkit of modern management products – including testing systems and probiotics to supplement the overall treatment of fish ponds.
Within our line of aquaculture probiotics, we have several products designed to make it easy for farmers to proactively manage their ammonia levels. PowerSludge, a tableted probiotic blend, is designed to reduce the waste build-up on the bottom of fish and shrimp ponds - a major source of ammonia. PowerPond and PowerShrimp are water probiotics with several bacteria strains focused on bio-remediation of the pond water. Together, these products provide farmers with low-cost, all-natural tools for ammonia control.
If you’d like to discuss these products, our sales team is here and ready to chat with you!