Here is a great example what Purigen can do if this is not cleaned.....
We had a big event a little earlier where we rescaped almost all of our tanks.
After they cycled they get back on track except one. A 180L tank.
This has an Eheim Prof 3 600 filtration only with bio media and 2 bags of Purigen (total 200g).
The filter used in the earlier scape, and after the rescape we cleaned the filter but not cleaned the purigen in it. Both was dark completely.
set up nov 12
HD9A7571 by
viktorlantos, on Flickr
dec 2
in the first 2 weeks we did like 10 water changes. filter clean, filter floss replacement.
and since nothing changed we added in a large UV filter if this happens for bacterial reason.
not helped.
Shots from our Showroom by
viktorlantos, on Flickr
Shots from our Showroom by
viktorlantos, on Flickr
the left tank was re-scaped the same time so there you can see how all other tanks cleaned up nicely.
at this point we were not sure if the cloudiness caused by the geotextil we used in the scape to hold the soil or something else.
opened the filted once more to check and replaced the Purigen to 2 new bags. 1 day after the replacement the water become clear
dec 16th shot after purigen replacement
Green Aqua Showroom by
viktorlantos, on Flickr
the 2nd day it cleaed up fully. sorry for the bad iphone shot.
http://akvakertesz.hu/threads/green-aqua-fotooezoen.1587/page-152#post-230715
maybe with a matured tank you do not see that much difference, but the filter medium not works the same way for sure.
so worth that little time to clean these bags.
We usually recommend 100g per 100L with this cleaning should be in every 3 months.