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Filtration & Pumps


December 13, 2018 | By Eric Nadon

An aquarium is an artificial environment, a replica of a natural ecosystem. This closed system lacks many of the organic filtration processes that occur in nature.

In natural water systems, since the amount of organic pollutants – such as waste excretion, uneaten food and decaying plant matter – is relatively small compared to the volume of water, it gets diluted over time. In addition, water is continuously replenished with rainwater. It’s nature’s version of a water change! This is not the case with an aquarium where waste stays in the tank. If pollutants are not removed via water changes or with a filter, the water quality is compromised.

Approximately 80 to 90% of all fish diseases are caused by physical stress, and the most common source of stress is from living in polluted water. Filtration is the backbone of an aquarium and is key to a healthy and thriving aquatic environment. In short, a good filtration system will create a successful aquarium.


In nature, a delicate balance between production and decomposition exists due to the biodiversity that naturally occurs in a healthy aquatic ecosystem. The process involves living and non-living parts, which interact with one another to create a stable system. Water filtration is a natural and essential part of this system.

Examples of natural filters / filtration processes include:

  • Soil / rocks
  • Wetlands and aquatic plants
  • Biotic reefs
  • The Nitrogen Cycle


Water is filtered as it moves through soil and rock. Firmly-packed particles filter out impurities and absorb excess nutrients such as nitrogen and phosphorous from water. Essentially, soil and rock act as a natural filter pad.


Wetlands act as filters to help reduce the amount of toxic compounds that enter a body of water. Plants found in these wetlands will absorb many of the harmful compounds into their roots and convert them into less harmful substances. In addition, toxic compounds can be deposited in the wetland’s soil where bacteria and other microorganisms will break them down. Aquatic plants naturally filter water by absorbing toxic metals and allow beneficial bacteria to grow. They also absorb ammonium, nitrates and phosphates from water and add oxygen.


A variety of biotic reefs exist in nature, including oyster reefs and tropical coral reefs. Reefs are home to a variety of filter feeders, such as micro-crustaceans, oysters, and sponges: an adult oyster can filter as much as 60 gallons of water a day! These filter feeders consume particulate matter suspended in the water, an essential filtration process which contributes to water quality.


The nitrogen cycle is a naturally occurring biological process that removes toxic compounds, such as ammonia, nitrite and nitrate, from water. It’s the means by which waste is converted into less harmful substances, keeping water free from toxic compounds. This process enables all bodies of water, such as lakes, oceans, seas, ponds, and streams, to sustain life.

The Nitrogen Cycle at work:

  • The cycle begins when fish waste, decaying plants, and other decomposing organic matter release ammonia into the water. Ammonia is toxic to fish and other aquatic inhabitants.
  • The conversion of ammonia into a less toxic compound is driven by nitrifying bacteria, which can be found on the surfaces of rocks, aquatic vegetation, gravel, and sand.
  • Nitrosomonas converts ammonia into nitrite. Nitrite is also toxic to fish and must be removed or changed. This is where the second group of nitrifying bacteria, nitrobacter, comes into play. Nitrobacter converts nitrite into nitrate. Nitrate is non-toxic to fish in small quantities and is used by plants as fertilizer.
  • Algae and aquatic plants use nitrate to produce chlorophyll, which in turn is consumed by fish. This completes the cycle, which then repeats itself.


In nature, filtration occurs as part of the hydrologic cycle (also known as the water cycle). This cycle involves 10 steps:

  1. Evaporation: the conversion of water from a liquid to a gas.
  2. Transpiration: the evaporation of liquid water from plants and trees into Earth’s atmosphere.
  3. Sublimation: this is the process where a solid, such as ice, changes into a gas without moving through the liquid phase.
  4. Condensation: this is the process where water changes back into a liquid.
  5. Transportation: the movement of solid, liquid and gaseous water throughout the atmosphere.
  6. Precipitation: this is water that falls to the earth.
  7. Deposition: water vapor (a gas) changes into ice (a solid) without going through the liquid phase.
  8. Infiltration: the movement of water into the ground from the surface. Percolation is movement of water past the soil going deep into the groundwater.
  9. Surface flow: the flow of water from rivers, lakes, and streams to the oceans. The water may return to the surface in springs or eventually seep into the oceans.
  10. Plant uptake: this is water taken from the groundwater flow and soil moisture.


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