Followup Fluval 3 internal filter

Hi
just to share what I discovered. Recap - flow was reduced to a trickle
one week after cleaning. Suspected impeller. Bought new one. No change.
So I replaced filter pad and all OK. Previously I squeezed out the pads
once a week and all was fine but recently the flow slowed to a trickle
after a few days.
On further investigation I cleaned the pad really thoroughly and was
amazed at the amount of solid material that came out, not the usual goop
but lots of fibrous material. Why the difference? On reflection I
realised that this only started happening since I changed the substrata
from gravel to sand. It seems that previously all that fibrous material
was finding its way into the gravel substrata but since changing to sand
it was ending up in the filter. So mystery solved. Anyone need a spare
impeller?
Thanks anyway to all who replied.
Regards,
Paul.
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Paul reply-to is valid