amphipods making home in purigen The Bag

[RioReefr]

So, I used one those Purigen Bags (designed for 100 G).

What I find strange is SeaChem says they are 180 microns and amphipods are clearly much larger than this. I have no idea how they got inside and even more puzzling why they seem to thrive. I guess of all the places in my tank, why would they chose that material?

Purigen lasts a very very long time, so no need to remove it just that I find bewildering.

 

[Oldreeferman]

Maybe the baby ones passed thu then molted & developed into adults later feeding on detrius?