Do Cory Catfish Need A Filter?

Cory catfish need a filter to survive in a freshwater fish tank. Cory catfish are tropical freshwater fish that needs clean, clear, fresh water to live optimum lives. Denying cory catfish a tank filter will result in various issues, including a short lifespan.

Tank filters remove toxins such as ammonia and nitrate from the water. Elevated levels of toxins in freshwater fish tanks will kill off cory catfish.

Cory Catfish Need A Filter

All cory catfish species originate from freshwater rivers in South America and are popular fish to keep in freshwater fish tanks. However, keeping cory fish safe and healthy requires filtering their tank water.

When in doubt if your fish needs a filter in the tank, remember the following. All fish that come from streams or rivers will die without filters. Besides purifying the water, filters create a current in the fish tank.

The current that filters create within the fish tank mimics that of rivers. The movement of water circulates oxygen through the fish tank.

Cory Catfish in Front of Plants

Why Cory Catfish Need A Filter

One must understand the nitrogen cycle inside an aquarium to fully grasp the importance of a filter in a freshwater tank containing cory catfish.

The nitrogen cycle in an aquarium

works as follows.

  • Fish excrements in the water after eating. The excrement releases ammonia which is very bad for fish. Ammonia is a toxin that can lead to fin rot, burnt gills, and other health issues.
  • Bacteria eat the ammonia turning it into nitrites. Bacteria can be added to the aquarium, and live plants can host bacteria for this purpose.
  • In due time the fish tank will contain levels of ammonia and nitrites. At this point, another bacterium comes into play that breaks down nitrites into nitrates.
  • Nitrites are fifty percent healthier than ammonia, but excess amounts are still harmful. Therefore, bacteria need to break down nitrites into nitrates.
  • Excess nitrates can be removed by a water change, while live plants also assist in removing nitrates.

The bacteria that break down these toxins live in the filter, substrate, glass, and tank ornaments. Filters trap the solid waste, converting liquid waste into a relatively harmless substance before the byproduct gets rereleased.

The Purpose Of Aquarium Filters

The filter and bacteria work together to clear the water of toxins and debris.

  • Filters remove the build-up of ammonia and nitrate from freshwater fish tanks. Freshwater fish, such as cory catfish, will die of poisoning within seven days if their water is not filtered.
  • Some filters also aerate the water. These filters create currents that circulate oxygen throughout the tank, which enables cory catfish to breathe properly.
  • Filters create movement in the water. Circulating the water is essential for distributing gasses and nutrients through the tank, making it accessible to all tank dwellers.
  • Cory catfish do not fare well in murky water conditions. So filters clear the water from debris, leaving it clear and keeping it fresh.
  • Filters are primarily home to beneficial bacteria. Beneficial bacteria must thrive since they are crucial for the health and well-being of the plants and fish inside the tank.

In essence, water filters are the digestive system of every freshwater fish tank. Cory catfish and their tank mates rely on filters to clean their water to stay healthy and happy.

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What Kind Of Filters Does Cory Catfish Need

Basic aquariums, such as the one cory catfish will be kept in, require two types of filters: mechanical and biological. Another option to consider is a chemical filter.

Mechanical Aquarium Filters

Mechanical aquarium filters literally trap solid waste and particles from the water. As a result, mechanical filters leave the water clean and clear. However, the mechanical filter must be removed from the tank and cleaned regularly to remove any waste from the water.

Biological Aquarium Filtration

Biological filters provide a place for bacteria to live and multiply. Biological filtration is the action of bacteria to break down ammonia into nitrites and nitrates, called the nitrogen cycle, which is explained earlier in the article. Biological filtration is, therefore, a natural process.

Biological filters should be checked regularly to ensure they are not clogged up by solid waste and particles that may have escaped the mechanical filter. Clogged biological filters are less effective.

Chemical Aquarium Filters

Activated charcoal and filtering resin are chemical filters that clean water and remove pollutants and harmful waste. Chemical filters are also referred to as nitrate and phosphate removers.

There are many filters on the market, and what you install will depend on the size of the tank, what type of fish you will keep, how many fish you will keep, and personal preference.

What Size Filter Does Cory Catfish Need

The tank size will determine the size filter needed. The aim is to install a filter that can recycle all the water three to four times every hour. A fifty-gallon tank, for instance, will need a filter capable of cycling one hundred and fifty gallons per hour to remove impurities effectively.

Cory Catfish Need A Water Pump

All fish needs oxygen and can only derive it from the water they live in. To plainly explain the need for water pumps, you need to imagine a body of stagnant water. Once water circulation halts, everything that lives in the water starts dying. Plants, fish, and crustacea suffocate due to a lack of oxygen circulation within the water.

The same happens to an aquarium in the absence of water pumps. Water pumps circulate oxygen throughout the tank and, along with filters, keep the water fresh, healthy, and clear. Always ensure the water pump in your tank functions properly and clean them as often as required.

How To Prevent Cory Catfish Deaths

Cory catfish are hardy for their size, and fish enthusiasts enjoy keeping them. Things you can do to help cory catfish live long, happy lives.

  • Adequately filter their water using both bacterial and mechanical filters. Besides food, filtering is one of cory catfish’s most critical needs.
  • Please provide them with enough food. These fish are bottom dwellers, and you need to take extra care to ensure they eat enough. Fish in the upper parts of the tank may scavenge food before it reaches the bottom. If need be, place food on the substrate for them to enjoy.
  • Cory fish originates from freshwater streams and enjoy clean, clear water. Therefore, water aeration is vital to keep oxygen moving through the tank.
  • Since cory catfish are bottom dwellers, they enjoy the protection of plant substrate. In addition, living plants provide cory catfish with cover, a resting place, and a safe place away from more aggressive tank mates.
  • The ideal tank size to keep cory catfish is fifty gallons.


Cory catfish have an average life span of ten to fifteen years depending on their tank conditions. The healthier the tank, the healthier and happier the fish will be. Proper filtration, healthy food, and sufficient oxygen are crucial to cory catfish longevity!