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Chlorine scare from new filter?

A

alar01

New Member
Joined
24 Feb 2025
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Hi all! I just had a scare with my main 20 gallon tank and I wanted some opinions.
I also want to preface this by saying my house is on well water, and we don't have added chlorine.

Yesterday afternoon I added a new Oase Biomaster 2 Thermo 250 to my 20 gallon tank. I put the Seachem matrix and Fluval rings from my last filter in the bottom basket, kept the 2 blue sponges in trays 2 and 3, and the polishing sponge in the short 4th tray. The bottom basket also has rinsed Purigen to reduce the tannins. I set everything up, washed the sponges in homemade RO water, and got it filtering. The prefilter has 2x 30ppi sponges and 2x carbon infused sponges that same with the filter, all washed with RO as well.

I noticed my Pencilfish acting a little bit weird this morning (sitting still under leaves, fanning their gills), but though it was only a reaction to increased flow and foreign tubes in the tank. Well... tonight I though to check with a test strip, and my water had chlorine around/under 0.8ppm! When I saw that put in an airstone and I sped to my local grocery store and picked up some API Tap Water Conditioner (I don't have chlorine in the well water or even have bleach in the house, so I didn't need to have it on hand), and after adding around 8mL and waiting 5 minutes, the test strips no longer show chlorine. The fish also seem to be more active, but still similar behavior.

Can someone help me make sense of this? The Purigen smells like chlorine, but I bought the bottle new and rinsed it before putting it in the filter. The filter itself had no smell at all. I use EasyGreen as my fert... Could that have reacted with the Purigen (something with amines maybe) and generated chlorine/chloramine? The Biomaster instructions didn't say to rinse the unit, or remove any of the excess silicone grease. Could that be the culprit?

All opinions are welcome. Hopefully this is just something simple that other beginners could also use hearing! Thanks
 
alar01 said:
I also want to preface this by saying my house is on well water, and we don't have added chlorine ...

The bottom basket also has rinsed Purigen to reduce the tannins. I set everything up, washed the sponges in homemade RO water, and got it filtering. ...

I noticed my Pencilfish acting a little bit weird this morning (sitting still under leaves, fanning their gills), but though it was only a reaction to increased flow and foreign tubes in the tank. Well... tonight I though to check with a test strip, and my water had chlorine around/under 0.8ppm!.

Can someone help me make sense of this? The Purigen smells like chlorine, but I bought the bottle new and rinsed it before putting it in the filter.
Click to expand...
I'll just take a guess.
The test strips show correct results.
The Purigen smells like chlorine.

I assume that the Purigen is the cause. It is best to remove it immediately and check it. What does it smell like? Does a test strip show a reaction?
 
alar01 said:
I put the Seachem matrix and Fluval rings from my last filter in the bottom basket, kept the 2 blue sponges in trays 2 and 3, and the polishing sponge in the short 4th tray. The bottom basket also has rinsed Purigen to reduce the tannins. I set everything up, washed the sponges in homemade RO water, and got it filtering. The prefilter has 2x 30ppi sponges and 2x carbon infused sponges that same with the filter, all washed with RO as well.
Click to expand...

I can’t help but just to say the water flows upwards so shouldn’t your Biomedia and Purigen be in one of the upper trays?
 
Teleos said:
I'll just take a guess.
The test strips show correct results.
The Purigen smells like chlorine.

I assume that the Purigen is the cause. It is best to remove it immediately and check it. What does it smell like? Does a test strip show a reaction?
Click to expand...
I removed it last night, right after posting. It seemed to be the only culprit. The bag of Purigen out of the filter didn't smell like anything.
I also did a quick experiment and put a teaspoon of the Purigen+ROwater in a beaker, and a control of only RO in another. I sealed the Purigen one with some clingwrap. This morning the air in the beaker smells the same as the bottled Purigen, but the test strip shows 0 chlorine. Any other tests to try with it? I'll bring it to my LFS today and ask if it seems normal... I've never bought Purigen before, so I don't have anything to compare it to.

Tank water thankfully shows 0 chlorine today as well. Pencilfish are looking more active, and my Panda Garra, Amano and Ramshorns don't seem affected.

I think my mistake was . . . TRUSTING AMAZON! When I got the Purigen in, it came in a badly crushed box. The metal seal was open on the bottle, but I thought it was popped open from getting smashed. Maybe it was used?

Aqua sobriquet said:
I can’t help but just to say the water flows upwards so shouldn’t your Biomedia and Purigen be in one of the upper trays?
Click to expand...
Ahh, that makes sense. We'll see if I ever trust Purigen again...
 
hypnogogia said:
How did you regenerate and rinse the purigen? Did you regenerate in bleach and not rinse in a chlorine neutraliser afterwards? I'd remove it immediately.
Click to expand...
Just rinsed in RO water. I didn't regenerate the Purigen, as it shouldn't have been used. This was 'new' from bottle poured into a mesh bag. Definitely already removed!
 
Hi all,
hypnogogia said:
How did you regenerate and rinse the purigen? Did you regenerate in bleach and not rinse in a chlorine neutraliser afterwards?
Click to expand...
I'd guess that is the source of the chlorine (Cl2), but not by @alar01?
alar01 said:
I also want to preface this by saying my house is on well water, and we don't have added chlorine. ......... I don't have chlorine in the well water or even have bleach in the house, so I didn't need to have it on hand
Click to expand...
cheers Darrel
 
alar01 said:
I removed it last night, right after posting. It seemed to be the only culprit. The bag of Purigen out of the filter didn't smell like anything.
I also did a quick experiment and put a teaspoon of the Purigen+ROwater in a beaker, and a control of only RO in another. I sealed the Purigen one with some clingwrap. This morning the air in the beaker smells the same as the bottled Purigen, but the test strip shows 0 chlorine. Any other tests to try with it? I'll bring it to my LFS today and ask if it seems normal... I've never bought Purigen before, so I don't have anything to compare it to.

Tank water thankfully shows 0 chlorine today as well. Pencilfish are looking more active, and my Panda Garra, Amano and Ramshorns don't seem affected.

I think my mistake was . . . TRUSTING AMAZON! When I got the Purigen in, it came in a badly crushed box. The metal seal was open on the bottle, but I thought it was popped open from getting smashed. Maybe it was used?


Ahh, that makes sense. We'll see if I ever trust Purigen again...
Click to expand...

I use Purigen in both of my filters. An Eheim Classic 350 and a Biomaster 350. No problems so far. One tank in particular was pretty yellow before due to tannins from some bogwood. All nice and clear since using the Purigen.
 
What is Purigen supposed to smell like? Does it have a scent out of the package?
The image printed on the outside of the bottle doesn't match the color of the contents, the Purigen itself is a little more yellow.
 
alar01 said:
I think my mistake was . . . TRUSTING AMAZON! When I got the Purigen in, it came in a badly crushed box. The metal seal was open on the bottle, but I thought it was popped open from getting smashed. Maybe it was used?
Click to expand...
Yes, maybe it was used. And small quantities of Cl were still there.
 
Thinking out loud here, but Purigen regeneration takes me no more than 30 minutes. I am a bit wary about whether I’ve rinsed and soaked it in Sodium Thiosulphate for long enough. I’ve not had any problems so far, but I must remember to leave the bag in some rainwater afterwards and check for Chlorine next time. I’ve got some multi test strips.
 
Teleos said:
No dust, not new.
Click to expand...
That's a good indicator, as there was near zero dust when rinsed.

Aqua sobriquet said:
I’ve not had any problems so far, but I must remember to leave the bag in some rainwater afterwards and check for Chlorine next time. I’ve got some multi test strips.
Click to expand...
Definitely do! From some reading it seems that anything below 0.4ppm chlorine doesn't give off any scent, but a level of even 0.05ppm can be toxic/damaging gills.
 
alar01 said:
That's a good indicator, as there was near zero dust when rinsed.
Click to expand...
I think you have got a mixture of new and regenerated Purigen. Or regenerated only.

I regenerate Purigen with a mixture of bleach and warm water in a sealed jam jar. This process is completed after 30 minutes at the latest. It is then rinsed well with warm water. This removes most of the Cl. It then remains in the jar until the next use. Before it is used again, it is soaked in water with vinegar or ascorbic acid for a short time. You can then test it for Cl with a test strip. I also test it for several hours in a beaker with aquarium water and some invertebrates. There has never been a loss of any living organisms.

Essential: You know what happens when you use bleach and an acid. Do not imitate if the consequences are not clear.
 
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Some aquarists have 2 or 3 bags of Purigen in the filter without issues at all, could be a dodgy delivery, it needs to be well above the sponges last basket before water goes back in aquarium otherwise it would get clogged up . Thinking maybe you have lost beneficial bacteria with the changes. Keep up with water changes
 
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