What Is the True Meaning of Total Organic Matter (TOM) in a Shrimp Pond?
By Author: Dr.Wiphada Mitbumrung, Ph.D. Applied Marine Biosciences — Thu Apr 30 2026
Total Organic Matter (TOM) is one of the most commonly used parameters in shrimp farming, yet it is also one of the most misunderstood. Many farmers associate TOM only with waste accumulation or “dirty pond bottom,” but from a scientific perspective, TOM represents a much broader concept. It includes not only waste materials but also living and non-living organic components within the pond ecosystem. Understanding what TOM truly means, how it is measured, and how to interpret it correctly is essential for effective pond management and decision-making.
Total Organic Matter refers to all carbon-based compounds present in the pond system. These compounds originate from multiple sources, including uneaten feed, shrimp feces, dead plankton, microbial biomass, and dissolved organic compounds released during biological processes. Organic matter can exist in both particulate form, such as visible sludge or suspended particles, and dissolved form, which is not visible but still actively participates in chemical and biological reactions in the water. In a shrimp pond, TOM is therefore not just waste. It is a combination of both productive organic matter and non-productive or accumulated waste. Productive organic matter includes living organisms such as phytoplankton, zooplankton, beneficial bacteria and benthic microorganisms that contribute positively to the pond ecosystem. These components play important roles in nutrient cycling, oxygen production, and natural food availability. On the other hand, non-productive organic matter includes decomposing feed residues, fecal waste and dead organisms that accumulate over time and can lead to deterioration of water and soil quality.
The titration method commonly used to measure TOM in shrimp ponds is usually the Walkley-Black method. However, this method does not directly measure total organic matter in the whole pond water. Walkley and Black Organic Carbon SOP is a classic analytical procedure designed to measure Soil Organic Matter (SOM) in soils/sediments through quantifying Carbon in the given sample, where it estimates organic carbon, and then that value is converted into organic matter. So when people say they measured TOM by titration, in most cases they actually mean organic matter in pond soil/sediment by dichromate oxidation titration. There are a few important limitations. First, the titration method measures oxidizable organic carbon, not every single form of organic matter perfectly. FAO notes that the original method recovers only about 77% of organic carbon on average, so correction factors are often applied. Second, in brackishwater or saline shrimp pond soils, chloride can interfere with the reaction and cause overestimation unless the method includes a chloride correction or treatment. This is very relevant for shrimp farming because saline pond bottoms are common.
So how should we interpret the result? A higher value means there is more organic material accumulated in the pond bottom. But it does not tell exactly what that material is. The titration method does not separate uneaten feed, shrimp feces, dead algae, benthic biomass, live probiotics, bacterial biofilm, or detritus. It simply measures the total oxidizable organic carbon pool in that soil sample. That means the number can include both waste and biological biomass. This is why TOM by titration should be interpreted carefully. A high TOM value does not automatically mean bad pond. It may indicate heavy accumulation of waste, but it may also reflect a biologically active pond with lots of settled organic biomass. What matters is whether the pond bottom can still process that organic load without turning anaerobic. It is also important to understand that not all organic matter is equally degradable. Fresh organic matter, such as recently added feed or active microbial biomass, is generally more labile and can be rapidly utilized by bacteria. In contrast, older or more complex organic compounds may be resistant to degradation and accumulate over time. This difference affects how TOM behaves in the pond and how quickly it can be managed through biological processes. In practice, farmers should interpret TOM together with pond bottom color, smell, sludge thickness, DO, ammonia, and ORP.