Last update: October 19, 2023

Diatoms in Aquariums: What Do They Eat & Best Management Tips

In my journey to better understand our fascinating world, I’ve spent a good deal of time diving into the realm of diatoms. Trust me, there’s a lot more to these microscopic algae than meets the eye. For instance, have you ever wondered what do diatoms eat? Or how do they eat? What do they even produce? Hold on to your curiosity, and let’s unearth the answers.

Diatoms are a type of microscopic algae that are found in both freshwater and marine environments. They are a critical part of the food chain and play a significant role in the global carbon cycle.

Despite their importance, many people are unaware of what diatoms eat, especially for diatoms in aquariums. Understanding the diet of diatoms is essential for understanding their role in the ecosystem.

Diatoms are unique because they are capable of both photosynthesis and heterotrophy. This means that they can produce their food through photosynthesis, but they can also consume other organisms for nutrients. 

The specific diet of diatoms varies depending on the species and the environment in which they live. Some diatoms are strict autotrophs, while others are mixotrophs that consume other organisms when nutrients are scarce.

Key Takeaways on Diatoms in Aquariums

  • Diatoms are a type of microscopic algae that play a critical role in the food chain and the global carbon cycle.
  • Diatoms are capable of both photosynthesis and heterotrophy, and their specific diet varies depending on the species and environment.
  • Understanding the diet of diatoms is essential for understanding their role in the ecosystem.

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What are Diatoms

Diatoms are unicellular, eukaryotic, photosynthetic microalgae that belong to the group of brown algae known as heterokonts.

They are single-celled organisms that are found in both freshwater and marine environments, where they play a crucial role in the food chain as primary producers.

Diatoms are part of the larger group of protists, which are unicellular organisms that are not classified as animals, plants, or fungi. They are classified as brown algae due to the presence of pigments in their cells that give them a brownish color.

Diatoms are known for their unique cell walls, which are made of silica and have intricate patterns that are specific to each species. These patterns have made diatoms useful in a variety of applications, including as indicators of water quality and in the production of nanotechnology.

As autotrophs, diatoms use photosynthesis to produce their own food from sunlight and carbon dioxide. They are a major component of phytoplankton, which are microscopic plants that float on the surface of the water and form the base of the food chain in aquatic ecosystems.

Diatoms’ Structure

Frustules and Cell Walls

Diatoms are unicellular organisms that are enclosed in a silica-based cell wall called a frustule. The frustule is composed of two overlapping halves, or valves, which fit together like a petri dish.

The frustule is porous, allowing for the exchange of gases and nutrients between the diatom and its environment. The frustule also provides protection against predators and physical damage.

Cell Size and Division

Diatoms are typically small, ranging in size from 2 micrometers to 200 micrometers. They reproduce asexually by dividing into two daughter cells, each with a new frustule.

The size of the daughter cells is determined by the size of the parent cell, with smaller cells producing smaller daughter cells.

Chloroplasts and Organelles

Diatoms contain chloroplasts, which are organelles that carry out photosynthesis. The chloroplasts are located in the cytoplasm, along with other organelles such as the nucleus and mitochondria.

The chloroplasts contain pigments that allow diatoms to absorb sunlight and convert it into energy. The pigments also give diatoms their characteristic brown color.

Diatoms’ Habitat

Diatoms are found in a variety of aquatic habitats, including freshwater and marine environments. They are a key component of the plankton community and play an important role in the food web of these ecosystems.

Freshwater Diatoms

Freshwater diatoms are commonly found in rivers, lakes, and other freshwater bodies. They are most abundant in surface waters, where they can receive enough light for photosynthesis.

Freshwater diatoms are often found in sediments, where they form a significant part of the benthic community.

Water quality is an important factor in determining the distribution of freshwater diatoms. Some species are more tolerant of pollution than others and can be used as indicators of water quality.

Marine Diatoms

Marine diatoms are found in a wide range of habitats within the marine environment, from the water column to sediments. They are most abundant in surface waters, where they can receive enough light for photosynthesis.

Marine diatoms are an important component of the marine food web, providing a source of food for zooplankton and other organisms. They are also important in the cycling of nutrients in the ocean.

There are two main groups of marine diatoms: pennales and centrales. Pennales are typically found in coastal waters, while centrales are found in open ocean environments.

Overall, diatoms are an important and diverse group of organisms that play a key role in aquatic ecosystems.

Photosynthesis and Nutrient Uptake

Light and Sunlight

Diatoms are photosynthetic organisms that require light for energy production. They use chlorophylls a and c to absorb light and convert it into chemical energy through the process of photosynthesis.

Diatoms are able to use both blue and red light, and they are able to adapt to different light conditions by changing their pigmentation.

Carbon Dioxide and Oxygen

Carbon dioxide is another essential component for photosynthesis in diatoms.

They use carbon dioxide from the atmosphere or dissolved in water to produce organic compounds, which are then used for growth and energy production. During photosynthesis, diatoms release oxygen into the environment, which is important for aquatic ecosystems.

Nitrogen and Other Nutrients

Diatoms also require other nutrients, such as nitrogen, phosphorus, and silica, for growth and reproduction. Nitrogen is used to produce proteins and nucleic acids, which are essential for cellular functions.

Diatoms can acquire nitrogen through different sources, including dissolved organic nitrogen and ammonium.

Silica is another important nutrient for diatoms, as it is used to build their frustules, which are the external structures that protect and shape the cells.

Diatoms are able to take up silica from the environment and incorporate it into their frustules, which are made of intricate and ornate patterns.

Reproduction and Growth in Diatoms

Cell Division and Meiosis

Diatoms reproduce asexually through cell division, which is the process of splitting one cell into two identical daughter cells. This process is known as mitosis and is the primary mode of reproduction in diatoms.

During mitosis, the diatom’s nucleus divides, and the cell’s contents are distributed equally between the two daughter addition to mitosis, diatoms also undergo sexual reproduction through meiosis.

Meiosis is the process of cell division that results in the production of gametes, which are specialized cells that fuse during fertilization to form a zygote. The zygote then develops into a new diatom cell.

Spore Formation and Movement

Diatoms can also reproduce through spore formation. Spores are specialized cells that are capable of surviving in unfavorable conditions and can germinate into new diatom cells when conditions become favorable.

Spores are formed through a process called sporulation, which involves the production of specialized cells that are resistant to harsh environmental conditions.

Diatoms are also capable of movement, which is essential for their reproduction. Movement in diatoms is facilitated by the presence of motile structures called flagella.

The flagella enables the diatom to move through the water, which is important for the dispersal of spores and gametes.

Diatoms in the Food Chain

Diatoms, being primary producers, are at the base of the aquatic food chain. They play a crucial role in the marine food web by providing food for herbivorous zooplankton such as copepods, krill, and other small crustaceans.

These zooplankton, in turn, are consumed by larger predators such as fish, marine mammals, and birds.

Diatoms are known to be an important food source for many marine animals. For example, the larvae of many fish species feed on diatoms during their early development stages. Some marine invertebrates, such as bivalves and gastropods, also consume diatoms as a part of their diet.

Apart from being a direct food source, diatoms also contribute to the marine food chain indirectly.

When diatoms die, they sink to the bottom of the ocean, taking with them the carbon they have absorbed during photosynthesis. This process, known as the biological pump, helps to sequester carbon from the atmosphere and store it in the deep ocean.

Diatoms and Climate Change

Diatoms play a crucial role in the global carbon cycle, as they are responsible for approximately 20% of the world’s primary production. As a result, any changes in their abundance, distribution, or physiology could have significant implications for the global carbon budget.

Climate change is one of the main factors that could affect diatoms and their role in the carbon cycle. Rising temperatures, changes in ocean circulation patterns, and alterations in nutrient availability could all have significant impacts on diatom populations.

One potential consequence of climate change is the alteration of the balance between diatom carbon fixation and export of carbon to the deep ocean.

If diatoms become less efficient at exporting carbon, this could lead to an increase in atmospheric CO2 concentrations and exacerbate global warming.

Another potential impact of climate change on diatoms is the alteration of upwelling patterns. Upwelling is a process by which cold, nutrient-rich water rises from the deep ocean to the surface, providing a source of nutrients for diatoms and other phytoplankton.

Changes in upwelling patterns could alter the availability of nutrients for diatoms, which could in turn affect their growth and productivity.

Diatoms in Forensic Science

Diatoms can play an important role in forensic investigations, particularly in cases of drowning.

When a person drowns in water, diatoms from the surrounding water can enter the lungs and bloodstream. These diatoms can be used as evidence to determine whether the person was alive or dead when they entered the water.

In forensic science, diatom analysis is often used in conjunction with other evidence to help establish the cause and manner of death.

Diatoms can be found in various parts of the body, including the lungs, liver, and bone marrow.

By analyzing the diatoms present in these tissues, forensic scientists can determine the type of water the person was in when they drowned, which can help narrow down the location of the drowning.

Diatom analysis can also be used to determine the time of death in cases of drowning.

By analyzing the diatoms present in the body and comparing them to the diatoms present in the surrounding water, forensic scientists can estimate how long the person was in the water before they died.

Types of Diatomaceous Earth

There are two key grades, and each has its own unique tale.

Filter Grade

So, there’s this thrilling escapade where diatomite undergoes a heating transformation, turning it into a filtering powerhouse. This process activates the silicon dioxide, making it crystalline silica. But hold on—this grade isn’t for casual strolls. It’s strictly for heavy-duty filtering applications, like in swimming pools. Why? Because crystalline silica is no joke; it can be hazardous to both humans and animals.

Food Grade

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Now, the gentler sibling hasn’t been through the same oxidizing ordeal. It’s the friendlier choice for things like animal feeds or even pest control in your home garden. If you’re thinking of ingesting it, though, I’d recommend making sure it meets the required heavy metal guidelines.

Diatomaceous Earth and Its Many Uses

Diatomaceous earth, or diatomite, is like Mother Nature’s Swiss Army knife, with various uses that I find pretty fascinating.

Filtration and Water Quality

Picture this: due to its porous nature, diatomaceous earth is an A-list filter medium, sifting out impurities like sediment, bacteria, and algae from water. It’s like the superhero of water filtration, showing off its skills in swimming pools, aquariums, and industrial water treatment plants.

Pest Control

The microscopic diatomaceous earth isn’t just here for its good looks. In the face of a flea infestation, it’s like Mother Nature’s own pest control. I find it kind of poetic—this fine powder attacking fleas at a cellular level, disrupting their waxy exterior, and leading them to their dehydrated demise.

Abrasives and Beauty Secrets

In the realm of household cleaning, diatomaceous earth takes the stage. It’s not just for scrubbing sinks—it’s made its mark in the beauty industry and dental care too. A sprinkle on your toothpaste, and you’ve got a smile that could rival any toothpaste commercial.

Indicator Species

Diatoms aren’t just ingredients; they’re practically the sentinels of aquatic health. I think it’s fascinating that being photosynthetic, they’re like the health barometers of ecosystems. Their presence speaks volumes about the well-being of an aquatic habitat.

At the end of the day, diatoms and diatomaceous earth are like unsung heroes. They pack in awe-inspiring functionality in such a minuscule form. If ever there was a reason to marvel at the intricacies of life on Earth, diatoms and their earthy byproducts would be high on that list.

Research and Future Directions

Research on diatoms and their diet has been ongoing for decades, and new discoveries are continuously being made. One area of research that has gained significant attention is the role of diatoms in the global carbon cycle.

Studies have shown that diatoms play a critical role in the transfer of carbon from the atmosphere to the ocean, making them a crucial player in mitigating climate change.

Future research directions in this area include understanding the mechanisms by which diatoms transport carbon, as well as the impact of environmental factors such as temperature and nutrient availability on these processes.

Additionally, researchers are exploring the potential for using diatoms as a biofuel source, which could have significant implications for renewable energy.

Other areas of research on diatom diets include understanding the role of specific nutrients, such as silicon and nitrogen, in diatom growth and metabolism.

Researchers are also investigating the impact of different types of grazing organisms on diatom populations, as well as the impact of environmental stressors such as pollution and ocean acidification.

Frequently Asked Questions

What is the diet of diatoms?

Diatoms are photosynthetic organisms that obtain their energy from sunlight. They are autotrophs, which means they can produce their own food through photosynthesis.

Their diet consists of inorganic nutrients such as carbon dioxide, nitrogen, phosphorus, and other minerals that they absorb from their environment.

How do diatoms obtain their nutrition?

Diatoms obtain their nutrition through photosynthesis. They use chlorophyll and other pigments to capture sunlight and convert it into energy.

They also absorb inorganic nutrients such as carbon dioxide, nitrogen, and phosphorus from their environment to build their cell walls and carry out metabolic processes.

What are the primary sources of food for diatoms?

The primary sources of food for diatoms are inorganic nutrients such as carbon dioxide, nitrogen, and phosphorus. These nutrients are found in the water and are absorbed by diatoms through their cell walls.

Some diatoms may also consume organic matter such as dissolved organic carbon and bacteria.

Can diatoms consume other organisms?

Diatoms are not known to consume other organisms. They are photosynthetic organisms that obtain their energy from sunlight and inorganic nutrients.

However, some diatoms may interact with other organisms in their environment, such as bacteria and zooplankton, in a variety of ways.

What nutrients do diatoms require for growth?

Diatoms require inorganic nutrients such as carbon dioxide, nitrogen, phosphorus, and other minerals for growth.

These nutrients are absorbed from their environment and are used to build their cell walls and carry out metabolic processes. The availability of these nutrients can affect the growth and productivity of diatom populations.

What role do diatoms play in aquatic food webs?

Diatoms are an important part of aquatic food webs. They are a primary producer, meaning they are at the bottom of the food chain and provide food for other organisms.

They are consumed by zooplankton, which are then consumed by larger organisms such as fish and whales. Diatoms also play a role in the global carbon cycle by absorbing carbon dioxide from the atmosphere and converting it into organic matter.

Ian Sterling

Ian Sterling, founder of, began his aquarium journey over 30 years ago, driven by a deep fascination for fish and their diverse personalities. His website,, is dedicated to making fishkeeping accessible and enjoyable, offering beginner-friendly guidance, expert insights, and a community for aquarists to connect and share experiences.

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