How to regenerate Purigen
The filter medium Purigen, as a synthetic resin, takes care of crystal-clear water. It doesn’t only clear the water, but also removes organic nitrogen compounds. With time, Purigen will turn brown to black, which is an indicator for the Purigen to be renewed. This regeneration and reactivation can be done using (unscented) common household chlorine bleach.
Bagged Purigen in different states of saturation. Left: new, middle: slight use, right: after long-time use.
In principle, you proceed in a way similar to the method explained in this article on cleaning glassware. The manufacturer Seachem from the USA recommends a 8,25% household chlorine bleach. This should be diluted with water by about 50%. The common chlorine bleaches on the German market often only have a concentration of 5%. In this respect, you can use the low-concentrated bleaches undiluted or only slightly diluted. When handling chlorine bleach, the manufacturer's precautions should be followed. We recommend to wear gloves, use tweezers and work in a well-ventilated room.
Now a bath is prepared for the Purigen. For this, the bleach is put into a non-metallic vat and enough bleach should be used to completely submerge the Purigen. The handy thing here is, that the 100ml unit of Purigen already comes in a chlorine-proof bag. Bigger packing units (250 ml upwards) are sold as dry bulk and used in filter bags. If you use the original filter bag "The Bag" from Seachem, chlorine resistance is a given. If you have used foreign products, you should first find out if the bag is resistant to chlorine. If not, we recommend regenerating the Purigen without a filter bag.
The Purigen should stay in the bath for at least 24hrs. To make sure that all little Purigen balls are exposed to the chlorine bleach, the bag can just be turned over after roughly 12hrs. When processing loose goods, stirring the solution has the same effect.
The regenarion is complete, when the Purigen has turned back to its initial, white colour. However, it is not yet operational in this state. First, by thorough rinsing under running water, the chlorine residues need to be removed. A chlorine smell should not be noticeable anymore. The manufacturer Seachem also recommends, just to make sure, another 8hr bath in a solution made from water and water conditioner. This removes the last chlorine residues. However, one should take care not to use water conditioners that contain a special mucosal protection for fish. This is often based on aloe vera and can impede regeneration and permanently damage the Purigen. After another rinsing, the Purigen can be used again.