How to Customize Your Aquarium Filter with Filter Media

Aquariums can widely differ in their size and stocking levels, so it makes sense that people want the ability to customize the filtration to best suit their needs. Most filters – such as hang-on-back (HOB), corner box, internal, canister, and sump filters – can be modified by changing the types of filter media used inside. Filter media is the various layers of materials through which aquarium water is filtered before being returned to the aquarium. Keep reading to learn about the different kinds of media, the functions they serve, and which ones you should use.

1. Mechanical Filter Media

Mechanical filtration uses sponges, foam pads and filter floss to physically remove any debris from the water. It is similar to a coffee filter. The pores in mechanical media are porous, so water can still flow through them. Also, the size of the particles caught in the material determines how big they will be.

Sponge pads made of coarse sponge

with large pores are good for blocking most debris like fish poop and dead leaves, and when they become full of waste, you can squeeze them out in old tank water and reuse them over and over again. You don’t need to keep them clean as they don’t clog quickly. To replace disposable filter cartridges in aquarium kits, we often use sponge pads.

If you’re still seeing tiny particles floating in the aquarium and want to get crystal clear water, try adding a fine poly pad or filter floss. This mechanical filter media can trap the smallest particles of flotsam, jetsam, and other debris in your aquarium. The floss pads are extremely dense and can cause clogging. They should be replaced if they become brown. Both the coarse sponge pad and fine poly pad can be customized by cutting them into smaller sizes so that they fit your filter perfectly.

Fine poly pad (left), and coarse sponge pads (right) are used for mechanical filtration.

2. Biological Filter Media

Biological filtration refers to the usage of beneficial bacteria and aquarium plants to consume the toxic nitrogen chemicals generated from fish waste, thus purifying the water. Because beneficial bacteria grows on any surface area in the tank that is well-oxygenated, the filter is a primary location to boost the population. Biological media (such

bio rings

Bio balls (or bio balls) have porous or intricately-patterned surfaces that provide “housing” to the bacteria colony. Beneficial bacteria can also grow on the sponge pads that are used for mechanical filtering. Bio media’s shape allows water to flow freely through them, which in turn brings more oxygen to the bacteria. Aquarium gunk can cover these surfaces over time, so clean the bio media every 1-3 months by gently waving or rinsing it in old tank water until the debris falls off. (If you are using loose bio media that does not come in a bag, put it in a filter media bag to make it easier to pick up and clean.)

Aquarium bio rings for biological filtration

3. Chemical Filter Media

Chemical filtration is able to remove contaminants and some chemicals from water. The most popular type of activated carbon is a porous charcoal that absorbs drugs, tannins and other impurities. Activated Carbon for Aquariums is typically supplied loose granules that must be placed in a filter bag. We prefer using

Carbon-infused media pads

They are easy to use, can be cut to a desired size, and provide mechanical filtration for straining water debris. You can even cut out a section of the pad to wrap around a sponge filter with a rubber band or zip tie for added chemical filtration. Once the charcoal pores become clogged up with pollutants, activated carbon media cannot be used again and must be replaced.

You can also get synthetic adsorbents like Purigen if you prefer chemical filtration. The polymer granules come pre-packaged in a media bag, ready to absorb organic waste and tannins. Once the adsorbent changes color from off-white to dark brown, the pores in the polymers have become saturated and must be cleaned. To clean the Purigen bag, follow the manufacturer’s instructions. Use a bleach solution to burn off organic impurities.

Filter media can be designed to filter out certain chemicals. For example, ammonia spikes are prone to occurring when the balance of your fish tank has been disrupted, such as after moving an aquarium, experiencing a power outage, or thoroughly cleaning a fish tank. To prevent toxic levels of ammonia from building up, you can preventatively install an ammonia filter pad to absorb the ammonia and keep your fish safe.

If phosphate levels are excessively high in your aquarium, it can lead to algae growth and compromise your fish’s health. To keep the phosphate levels under control, you can use a phosphate media pad. This will prevent algae from taking advantage of it. Some articles on aquariums recommend that you keep a phosphate level of 0.5 to 2.0 ppm for healthy growth. Otherwise, the leaves may yellow and become brown.

Carbon-infused, ammonia, and phosphate pads for chemical filtration

Filter Media FAQs

Which order should I place the aquarium filter media in?

There are many options for how to layer the filter media inside your filter. We have listed some of our suggestions. The first step is to look in the manual and find out which direction the water flows through the filter. We like to use a coarse sponge to filter out large particles of debris as they enter the filter media basket. If you need to use the ammonia or phosphate media pads, you can place them here since the pads also serve as mechanical filtration. To capture smaller particles suspended in water, you can also add the fine poly pads to your final mechanical filter layer.

The next layer is the biological filtration, so fill the media trays with bio media. Finally, chemical filtration can be used at the end of the filter just before water exits the aquarium. Not all of these products are necessary, but we do recommend having at least one layer of coarse mechanical filtration and then one layer of biological filtration if you have room.

How can I clean an aquarium filter that doesn’t kill bacteria? Rinse the filter media in old aquarium water. Coarse sponge pads are the dirtiest and can be vigorously wrung to clean it as much as possible. Bio media houses beneficial bacteria and should be gently agitated (not scrubbed) in the water. Except for Purigen which can be washed with bleach, chemical filtration must be completely replaced. It depends on the size and media of the filter as well as the amount of food that is being fed to it. As a general rule, it is a good idea to set up a reminder in your calendar to clean your filters every 1-3 months.

Place loose media, such as activated carbon or bio media, in a filter bag to make it easy to transport and contain.

How long does aquarium filter media last? Reusable filter media – such as the coarse sponge pad, bio rings, and Purigen – can last for many years, as long as it can be cleaned sufficiently so that its functionality is not impaired. If fine poly pads turn brown and water can’t pass through them, they should be disposed of. You can only measure the water to determine if any chemical filtration such as activated carbon, ammonia pads, or phosphate pads has been used. If there are any tannins or unusual odors in your water, the activated charcoal should be replaced. If the water contains excess phosphate or ammonia, the chemical media pads will be ineffective.

Do I need carbon in my aquarium filter? Because activated carbon (and most chemical filtration) is disposable and cannot be reused, we like to save it for specific instances when we know there are pollutants or tannins that we wish to remove. To ensure that the aquarium water is crystal clear, carbon can be used if you’re preparing for a photo shoot. However, most hobbyists do not use carbon on a daily basis because it gets depleted so quickly and the results may be temporary.

To take your fish tank filtration to the next level, learn how to upgrade your aquarium filter with filter media in four easy steps.