aquarium filtration

All About Aquarium Filtration

What You Need To Know About Aquarium Filtration


If you are contemplating starting an aquarium of any kind, then you should also be considering what type of filter you will be providing your fish. Also, if you have never owned fish as pets before then you may be unaware of how much you need to know about their daily needs. Proper filtration is one of the main components in your aquarium’s overall health and wellness. We want to help you choose the best aquarium filter for you fish tank. This article will contain most of the information you will need in regards to an aquarium filtration system. So, brace yourself. Put on your seatbelt and hang on tight. This is going to be a heck of a ride!

aquarium filtration

What is Mechanical Filtration?

While this type of filtration is not discussed very much, it is still a vital role in the health of your aquarium. Mechanical Filtration is personally responsible for anything floating in the water. This could include uneaten food, debris, live plant materials, and waste. If it is solid, it will be caught by this process. Various medias are available for these filters including pads, filter floss, and combo cartridge. If the media has larger pores, then it will only catch larger floating materials. If the pores of the media are smaller (or fine), then it will catch most (if not all) of the physical debris floating in the water. In aquariums with goldfish, a mechanical filtration system with a fine pore media is recommended because goldfish are generally very messy fish. Be aware that fine media may clean debris from the water like a champ, but, it will also become clogged much quicker as a result. Therefore, it is vital that you clean your Mechanical Filtration System media regularly.

What are the various types of Mechanical Filtration media available today?

Filter Floss:

Also known as Filter Wool. These medias can be used in different kinds of filters. Although this method may seem old school, it works! Filter Floss is very coarse and will catch most anything physically floating in the water. This media would need to be cleaned or replaced quite often, but it would be worth it once you see the clarity of the aquarium water. Filter Floss can be used in Trickle Filters, Canister Filters, and Wet/ Dry Sump Filters.

Pads or Sponges:

These foam medias are commonly used in Power Filters and Canister Filters. The shape of the sponge will depend on the form of the filter basket. So, look at the filter basket before buying extra pads. While these medias can vary in pore size, they are often very fine and can clog quickly. To help prevent clogging or, to clean your sponge media simply remove it occasionally (or whenever it needs to be cleaned because it is clogged) and rinse the gunk out with treated tap water or tank water. Never rinse your filtration medias or anything for your aquarium with straight tap water as it is harmful to the fish.

Combo Cartridge:

            This media is a combination of Chemical Filtration (yet to be discussed) and Mechanical Filtration. As water approaches the outside of the filter, it is cleared of any physical floating debris by the Mechanical media. As the tank water passes through the cartridge, it is treated by the Chemical media inside. Be aware that some combo cartridges may need to be thrown out as opposed to reused. Before you buy a combo cartridge, read the manufacturer’s instructions to find out if it is reusable or if it must be discarded.

Tips about changing or cleaning your Mechanical media:

Mechanical Filtration medias collect physical debris from the water in your aquarium. As a result, they become clogged over time regardless of their pore size. It is your responsibility to care for your filtration media and keep them clear of debris to continue to allow water to flow through it. If a Mechanical media is left clogged, it will slow (and eventually halt) water flow and debris collection. This will result in a dirty tank, dirty water, harmful bacteria growth and therefore sick fish.

Remove a small amount of existing tank water and put it in a bucket. Eliminate the media and swish it in the tank water. Continue this process until most of the debris is gone. There will come a time when the waste does not come off as easily, and this is an indicator that it is time to replace the media. Most fine medias will not clean well and may need to be replaced rather than reused. Be careful not to clean or replace filtration medias too often. Beneficial bacteria may have developed in them and removing it could cause harm to the ecosystem. Also, if you are performing a tank cleaning do not replace the filtration media. Too much disturbance at one time could destroy the ecosystem that has been created.

What is Biological Filtration?

Biological Filtration is personally responsible for the breakdown of dissolved solids and turns them into a less toxic form. As this breakdown process continues, it builds an ecosystem of beneficial bacteria that then handle ammonia spikes and nitrite spikes. Without Biological Filtration media, the ammonia and nitrite levels would rise thus killing the aquarium inhabitants. Mechanical Filtration medias and Biological Filtration medias work hand in hand. No aquarium should ever be without either type of filtration.

These beneficial bacterias can either be ammonia-eaters or nitrite-eaters. The ammonia-eaters will take in the ammonia and then release nitrite. The nitrite-eaters will then use the nitrite released as their personal energy source. Avoid medications that are unnecessary, as well as, over-cleaning your aquarium or treating your aquarium with chlorinated water. These things will destroy any good bacteria that has developed in the Biological media.

What are the various types of Biological Filtration media available today?

The small medias are very porous and can handle greater surface areas. They are capable of housing more beneficial bacteria per small space. However, they are prone to clogging and are rather useless if they are not paired with a proper Mechanical Filtration media. For small aquariums, consider choosing a smaller media. Most Biological medias that are made from plastic are less likely to clog or need to be replaced.

Tips about changing or cleaning your Biological media:

Biological Filtration media should not need to be replaced unless it no longer functions from being too clogged. This will usually only occur if the Mechanical Filtration is not catching floating debris properly. Read the specific care instruction of the media you choose.

What is Chemical Filtration?

This type of filtration is not as common as Mechanical or Biological Filtration. However, Chemical Filtration medias are incredibly beneficial in regards to removing any chemical impurities in the tank water. These medias can either be Activated Carbon or Ion Exchange Resins. They remove unwanted matter that has dissolved and can cause harm to the aquarium inhabitants if not removed.

What are the various types of Chemical Filtration medias available today?

Activated Carbon:

Carbon contains tiny pores that can adhere to organic or non-organic materials. Choose new carbon for more efficiency. Once these small pores have all been filled this “new” carbon is now “old” carbon and is no longer useful for filtering chemicals. However, they are useful as Biological Filters. Carbon is perfect for removing dissolved proteins, carbohydrates, chlorine, copper, as well as, drugs and medications. If your fish are ill, and you must treat the water with antibiotics or other drugs, then it is best to remove the carbon filter before doing so. You can return it to the filter when treatment is over, and it can then help remove excess medications in the tank.


Resins attract individual molecules to them and become attached. Specific resins can remove dissolved organic materials, and other resins can attract nitrate or even ammonia.

More information about these filtration systems:

Most (if not all) species of fish should live in an aquarium or an outdoor pond that includes a good filtration system. This can be especially true for goldfish habitats because they are a messy species and require good quality water. Good filters will have a Mechanical Filtration media as well as a Biological Filtration media. The best filters will be fully equipped with all three media types (Mechanical, Biological, and Chemical). The filter that you need will depend on the tank that you choose.

What are the different types of filters available today?

There are many different types of filters for you to choose from. However, your choices will be narrowed as you decide what size aquarium you want to have.

  1.  Sponge air filter
      These are filters that draw water through a sponge
      This process is an excellent example of Mechanical Filtration as the floating debris will be caught by the sponge
      Beneficial bacteria colonies develop throughout this process
      These colonies provide Biological Filtration
      The size and shape of your sponge, as well as the pore size, will depend on what kind of aquarium you are considering
      Sponge filters are commonly powered by air pumps or power heads
      Lacks Chemical Filtration
      Not appealing in the tank (not pretty to look at)
      Easy to clean
      Last longer than most filters 

Sponge filters are the perfect choice of filter for:
  Small beta fish aquariums
  Aquariums specifically used for sick fish
  Fry (baby fish) aquariums
  Newly setup aquariums
  Shrimp Aquariums

Hang on Back filter: (also known as HOB filters)

    1. Very common amongst fish owners
    2. Easy to use
    3. Easier to clean compared to Canister filters
    4. Equipped with all three media types (Mechanical, Biological, Chemical)
    5. Water with physical floating debris is first filtered by the Mechanical media
    6. It is then broken down and filtered by the Biological media
    7. The Chemical media finally filters through the water for any chemical materials that are not wanted in the tank. The cleaned water is then returned to the main part of the tank
    8. Hang on Back filters are the perfect choice for:
      1. These filters can work well in almost any aquarium as long as the HOB is designed to handle that gallon capacity
      2. Perfect filter for hardy goldfish breeds that do not damage easily
        1. The Common Goldfish
        2. The Comet Goldfish
        3. The Shubunkin Goldfish
      3. Undergravel Filters
        1. Located beneath the layer of gravel of your choice or the gravel that is included in your aquarium starter kit
        2. Water is pulled under the gravel and into the filtration system which is beneficial towards Biological Filtration
        3. Inexpensive
        4. These filters are usually designed for Biological Filtration. However, some models have been designed with Chemical Filtration with added Activated Carbon or Mechanical Filtration with added Filter Floss
        5. Made for most aquarium sizes
        6. Undergravel Filters are the perfect choice for:
          1. Aquariums with a very little fish load
          2. Too many fish and fish waste in a single aquarium would be too much for this particular filter to handle
        7. Internal Filters
          1. Completely underwater placement
          2. Space saving
          3. Installation provides above normal water movement and filtration
          4. Filters out waste before it can reach and settle on the bottom of the aquarium
          5. Internal filters are the perfect choice for:
            1. Smaller aquariums (30-gallons and under)
          6. Canister Filters
            1. Known as the best filters for all three filtration medias
            2. Enormous in size
            3. Hard to clean
            4. Certain brands have low-quality designs and have been known to break or need refurbishing
            5. Crystal clear water quality results when the mechanism and medias are properly cleaned
            6. Difficult to setup
            7. Canister Filters are the perfect choice for:
              1. Large aquariums
              2. Lots of fish
  • African and South African Cichlid aquariums
  1. Saltwater aquariums
  2. Freshwater aquariums with live plants
  1. Wet/Dry Filters
    1. Amazing Biological Filtration
    2. One Biological media is exposed to the tank water, and the other is exposed to the air (hence the name Wet/Dry Filters)
    3. Require a lot of effort during setup
    4. Installation may be tricky and require multiple people to help
    5. Provides fish enthusiasts the opportunity to be creative
    6. May include a sump that contains equipment and the water return pump
    7. Wet/Dry Filters are the perfect choice for:
      1. Saltwater aquariums
      2. Large aquarium setups
  • Avoid for freshwater aquariums