Purigen – Amazing Filter Media And How To Use It (The Ultimate Guide)

This entry is part 5 of 6 in the series Filter media

Most aquarium owners opt out of owning purigen mainly because they have no idea how this filter media works or how to use it.


Simply put, purigen is a synthetic polymer that removes nitrogenous organic waste from your aquarium water. To determine if this filter media is right for your tank, it is essential you first understand how it works.  

1/ What is Purigen?

Purigen is a macro-porous synthetic polymer that helps to control ammonia, nitrite, nitrate, and other harmful compounds in your tank. It does this by removing the organic nitrogen waste in your aquarium water before they can decompose and release these harmful compounds.

The aquatic life in your tank, including plants, releases nitrogenous waste into your water. Purigen simply helps to remove such waste, and it does so at a fast rate.

Purigen can also remove discolorations in water, and leave your water looking crystal clear. In summary, purigen reduces water pollution and polishes your water to unparalleled clarity.   

>> Additional content: Check out our guide featuring:

1/ How to save your fish from ammonia & nitrite

2/ How to control your tank’s nitrate levels

2/ What kind of tank can use purigen?

Purigen can be used in both freshwater and saltwater tanks.

Purigen is recommended for a freshwater tank, especially when such a tank contains driftwood. Driftwood contains humic substances that often leaks into your aquarium water; these substances tend to cause water discolorations.  Purigen will help clear up your water and ensure it remains clear.

Purigen is also equally useful for saltwater tanks. Purigen is capable of absorbing the toxins released by the corals and anemones in your tank. This action will help purify your aquarium water and create a healthy environment for your aquatic life. 

3/ Why should you use purigen in your tank?

There are different types of filter media available on the market today, so you may be wondering why purigen? Well, not only does purigen have the ability to keep your tank clean, but it can also be regenerated.

The benefits of using purigen

Well, firstly, this filtration media can polish the water in your freshwater tank and leave it looking crystal clear at a rate faster than its counterparts. Purigen can perform this task without affecting the iron and other trace elements that are necessary for the growth of the plants in your tank.  

Also, in a saltwater aquarium, purigen will ensure your water is kept clean and clear. This will allow more light to reach your coral, which will cause them to thrive better.    

Ability to regenerate

Purigen, when used for an extended period of time, can turn black or brown.

This is the filter’s way of informing you that its absorptive capacity has been exhausted, and it needs to be regenerated.

The process of regenerating your purigen is easy, and you only require chlorine bleach. Regenerating your purigen after it has worn out will allow you to reuse it.

>> Click here to view chlorine bleach on Amazon.

4/ When should you use purigen for your tank?

Purigen should be inserted in a fully cycled tank and after the biological filter has been installed in the tank.

Placing your purigen in a tank before it is fully cycled can work against the cycling process. When your aquarium is fully cycled, there would be enough bacteria on the filter media, and sufficient waste would have been produced by the inhabitants of your tank.

As a result of this, the bacteria’s in your tank will not starve, and the purigen can simply help to control organic build up in your tank.

5/ How to use purigen in your tank?

How many purigen should I use?

The amount of purigen that should be used depends on the size of the tank. Generally, purigen that is 100ml in size is suitable for a tank holding up to 400 liters of water. Read the instructions on the package of the purigen to determine if it is suitable for your aquarium.   

Where and how to place your Purigen

Purigen can be placed in any filter, including external/internal filter, HOB filter and sump filter. Purigen should be inserted in an area where there is a strong current. Also, place your purigen in such a position that it would be the last filter the water passes through before it enters back into the tank.

>> For further information on 9 aquarium filter types, follow our guide here!

6/ Where to buy purigen?

Purigen can be purchased from a local pet fish store. This product is also sold by a variety of online stores, including Amazon. You can also click on the button below to view this product on Amazon.

7/ How long does purigen often last?

How long purigen can last before it needs to be regenerated will depend on the load of the tank. A clean and low stock tank can use this filter media for 4-6 months, while a fully stocked tank can only use it for a month before it turns brown.

8/ FAQs

Can purigen harm my fish and plant?

No, purigen is safe for your fish or plant. Although purigen absorbs organics which contribute to nitrate levels, it will not cause the nitrate to drop to a level so low that it will negatively affect your plants. So the plants in your tank will still have access to the adequate amounts of macronutrients they need.

Do I still need purigen if I am using protein skimmer?

No, it is not necessary. But if you have enough space in your filter and money, it is advisable to use purigen with a protein skimmer. Purigen will help to remove small nitrogenous organics that a protein skimmer can miss.

>> For more information on protein skimmer, follow our guide here!

Can purigen affect the pH of my tank?                                               

Yes, purigen can affect the pH of your tank, but this is only temporary. When purigen is placed for the first time in your tank or after it has been newly recharged, it can change the pH of your tank.

However, the change is more significant only in smaller tanks. To prevent purigen from affecting the pH of your tank, you can submerge the bag in a bowl of treated water and a powerhead for 24 hours. This helps to get rid of the buffering effect and allows you to add it to your filter safely.

>> Please take a moment and read my full guide about fish tank water pH.

Can purigen affect the hardness of the water in your tank?

This is dependent on several factors, such as if the purigen is brand new, the kind of fishes in your aquarium, and if your aquarium is fully stocked. A new package of purigen cannot lower the pH of your water, but newly regenerated purigen if poorly buffered can.

Does purigen remove ammonia, nitrite, nitrate, and phosphate?

Purigen does not directly remove ammonia, nitrite, and nitrate, but instead removes organic compounds that can decompose and release them. Purigen does not remove phosphate, so your aquarium plants still have enough micronutrients when needed.

Is there any alternative for purigen?

Yes, there are other alternatives, such as carbon. However, carbon is a chemical filter media and does not remove protein and other organics that a synthetic polymer filter media can. 

>> For further information on activated carbon for aquarium filter, follow our guide here!

Can I put too much Seachem purigen into my filter?

Yes, you can. Putting too much seachem purigen into your filter can have no adverse effect on your aquarium water. But it is advisable to put in just the right amount to avoid wasting the product.

Is it safe to use purigen alongside other aquarium products?

Generally, it is safe to use purigen with other aquarium products, but this is dependent on the product in question. There are various aquarium products on the market, so to determine if it is safe to combine purigen with another product, ensure you conduct adequate research on the product.  For instance, purigen can remove certain medications from your aquarium water, and as a result, you should avoid using purigen alongside such medications.  

If you remain unsure as to whether it is safe to use purigen together with another aquarium product, you can simply remove the purigen from your aquarium. Purigen can be stored for an extended period of time as long as it is kept wet and placed in a sealed container.

Series Navigation<< How to Change Your Filter Without Losing BacteriaHow to Regenerate Purigen (7 Quick and Easy Steps) >>