On my 120l I changed it after a month, but only found the outer beads to be brown. The latest lot has been in for three months now, so I may take a look this week. This tank is lightly stocked as well.
I am also using this product now. Not sure if i can say it has made an overwhelming difference to water clarity. Very hard to judge as i have loaches in my tank which do stir up some detritus at times. and usually fairly clear water anyway.
I need to dose Protozin in this tank now and i have heard that Purigen will remove the medication from the water, effectivelly treating it like a toxin - does anyone know if this is true?
Sorry Steve. I could have sworn I replied to your question.
I have added some wood to my tank, that turned the bucket water to tea ,while it was soaking. The tank water has stayed crystal clear, but I dare say the Purigen will become exhausted in double quick time.