Filter Media Aquarium product reviews

Seachem Purigen Review

seachem purigen

a review of Seachem Purigen – possibly the best filter media.

Seachem Purigen

Seachem Purigen is a product that I stumbled upon some time ago and have been using ever since.

Purigen is a synthetic filter media that is said to remove nitrogenous compounds from your water. This means that these compounds are removed before breaking down into ammonia, nitrite or nitrate.


Rather than me rambling on, here is Seachem’s description of their product direct from their site:

Purigen® is a premium synthetic adsorbent that is unlike any other filtration product. It is not a mixture of ion exchangers or adsorbents, but a unique macro-porous synthetic polymer that removes soluble and insoluble impurities from water at a rate and capacity that exceeds all other competing products by over 500%. Purigen® controls ammonia, nitrites and nitrates by removing nitrogenous organic waste that would otherwise release these harmful compounds. Purigen’s impact on trace elements is minimal. It significantly raises redox. It polishes water to unparalleled clarity. Purigen® darkens progressively as it exhausts, and is easily renewed by treating with bleach. Purigen® is designed for both marine and freshwater use.


seachem purigen




Unparalleled clarity?

Seachem Purigen will make your water crystal clear, or it will certainly help. As I’ve been using it for so long, I was struggling to remember how much of a difference it actually made. So for the last couple of months, I haven’t had any Purigen in my filter.

As a person who is affected by ‘aquarium OCD’, I noticed a difference. It isn’t that my aquarium water was dirty, as I keep to a pretty strict routine and always ‘over filter’, but there was a slight but noticeable difference in the overall clarity of the water.

Now, it is worth noting that Seachem Purigen alone will not keep your water crystal clear, for that you first need adequate filtration.

It is also worth noting that this aquarium is heavily stocked with CA cichlids and only had 2 Anubias plants in there at the time (they have since been destroyed by the fish). In a lightly stocked aquarium with good filtration and an abundance of plants, Purigen is unlikely to make a noticeable difference.

Below is a shot down the length of my 5-foot aquarium in which I use Purigen, as you can see, it’s pretty clear:


seachem purigen filter media



It’s Renewable!

Seachem Purigen is renewable. As it absorbs organic waste, Purigen darkens in colour, until, it turns completely black. Once it has gone black in colour, it is exhausted and can absorb no more. at this point, Seachem provides directions on how to renew it so that it is ready to use again:


Soak in a 1:1 bleach: water solution for 24 hours in a non-metallic container in a well-ventilated area and away from children. Use regular 8.25% hypochlorite household bleach (non-scented, no dyes, do not use a splash-less bleach).

Rinse well, then soak for 8 hours with a solution containing 4 tablespoons of Prime®, or equivalent dechlorinator per cup of water. Rinse well. For freshwater use, soak for 4 hours with a solution containing 2 tablespoons of buffer per cup of water (Discus Buffer®Neutral Regulator®).

Original colour and full activity should now be restored and Purigen® is ready for reuse. Caution: some slime coat products may permanently foul Purigen® and render regeneration difficult. Do not reuse if the odour of bleach/chlorine is detectable. In case of doubt, soak beads in a small quantity of water and test for residual chlorine with a chlorine test kit.


Does this work?

I have tried to regenerate Purigen a few times using this method. But if I’m honest I haven’t had a huge amount of success. After renewing it in this way I have found on more than one occasion that the Purigen still smelled ‘bleachy’, so I didn’t risk re-using it.

However, I have spoken to Seachem about this and they assure me that the regeneration process works so either:

1. I used too much bleach.

2. I was being a little over cautious.

The good news is that, even if you are being over cautious, Purigen isn’t too expensive and it takes a while for it to be exhausted. That means that it works out almost as cheap to simply replace the Purigen when it is used up. More often than not, that’s the option I use when it needs to be changed out.

To give an idea, I use Purigen in a 580-litre aquarium that is well stocked with messy CA cichlids. On average, a 200ml bag of Seachem Purigen will last around 4 months before being exhausted. Roughly £20 every 4 months isn’t too bad to help to keep my water crystal clear.


seachem purigen

Reduction of nitrogenous compounds

Seachem say that Purigen will absorb nitrogenous compounds before they break down into ammonia, nitrite and nitrate.

Unfortunately, I’m not equipped with a lab to fully test this but I would expect this to mean a reduction in nitrates.

Unfortunately again, I haven’t detected any reduction in nitrates whilst using purigen.

This would suggest that it is not able to absorb these compounds as suggested, or that it is and they still break down as they would anyway.

Should I buy some Purigen?

Seachem Purigen is a great addition to aquarium filtration but it isn’t 100% necessary.

Adequate biofiltration should do almost, if not as good a job and will keep your water nice and clean.

Purigen does do a great job of water polishing and tannin removal though and can help to keep your aquarium looking extra clear.

If you add some new wood to your aquarium but aren’t keen on the ‘Blackwater’ effect from the tannins then Purigen is ideal to soak them up. It does this very well!

Adequate and well set up filtration is all that is needed to keep your water clean and healthy, Purigen is an added extra for anyone looking for just a little extra clarity.

So, if you are considering giving it a go, click here. (As an amazon associate I earn from qualifying purchases).


Please note that Seachem Purigen is a back up to your regular filter media and shouldn’t be used as your only filter media. Whilst it absorbs Nitrogenous organic waste, it may not do as much for waste that has already been broken down into ammonia, nitrite or nitrate. So Purigen is an addition to your filter media, not your main media.

Disclaimer: This is not a paid review, like all my reviews this is my honest opinion from my own experience of using a product, it has not been influenced in any way.

About the author

James @Seriously Fishy

I am a fish keeping enthusiast with over 20 years experience. I currently keep American Cichlids (CA) which are my favourite fish to keep so far. I started Seriously Fishy as I noticed a large volume of people on various web pages looking for help with Aquarium basics. I created the first Seriously Fishy book to solve the issue in 28 pages, that led to the Seriously Fishy UK fish forum and blog.

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