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Seachem Purigen

Always clear water

The filter medium Purigen by Seachem is a unique product, that should in every aquarium. Whether community aquarium, planted aquascape or marine water reef, a use of this universally usable filter material is worthwhile in any case.

What is Purigen?

Purigen is a synthetic adsorption resin, based on a specific polymer. It is expressly not an exchange resin that absorbs and releases certain substances; it removes organic nitrogen compounds and other organic substances like proteins permanently from the water and reduces water pollution. Consequently, this increases the redox potential. In addition, discoloration of the water, which for example has been caused by using driftwood is effectively and quickly eliminated. After prolonged use, Purigen indicates the exhausted receptivity by an ever darker growing color. A clear shade of brown indicates that the filter medium should be regenerated.

Seachem Purigen

Purigen bagged in different states. Left: as new. In the middle: mild use. Right: after prolonged use.


Purigen can be used in any type of filter, outer filter, inner filter, techinical tank or filter shaft. Preferably, it should be placed in a well-flowed area. While the 100 ml version comes ready to use in a sealed bag, larger packages are available as loose items. Here the product should be placed in a suitable filter bag to match the size of the aquarium. The mesh size should not be too large, so that the tiny Purigen particles can not escape the bag. We recommend the filter bag The Bag by Seachem, which is re-sealable and chlorine-proof. This is important for the regeneration of Purigen, which we’ll cover later.

Purigen in a planted freshwater tank

Purigen is a great tool during the start-up of an acuascape or planted aquarium. Especially when driftwood was used in the design, which would turn the water brown thanks to the humic substances contained in the wood. Purigen keeps the water crystal clear from day one. Soil substrates such as ADA Amazonia, which emit quite a lot of nitrogen compounds into the water, are defused a bit by Purigen’s absorption capacity. Unlike activated carbon, it has no significant effect on iron and other trace elements important for the growth of aquatic plants. Although organic precursors of nitrogen-containing compounds are degraded, but Purigen does not directly remove nitrate, urea and phosphate. This leaves only macronutrients important to the water plants.

Purigen in the marine water aquarium

By removing organic compounds, Purigen supports the protein skimmer. After a certain runtime, the effect is noticeable by lower nitrate and phosphate levels in the open water. It removes the yellow tint of the aquarium’s water and ensures a crystal clear view. Coral growth gets enhanced, too because due to the clear water, more light will reach the corals. Unlike activated carbon, Purigen has close to no effect on trace elements and doesn’t remove them from the head of water in a way that’d make a difference. Purigen adsorbs nettle toxins emitted by corals and anemones and creates a better ambience for all inhabitants of the reef aquarium.


The performance of many other resins decreases over time, and regeneration can prove to be quite cumbersome. Purigen indicates its saturation through its hue which tends to turn more and more brown. It’s functionality is restored super easily using common household bleach. Detailed instructions can be found here.