EKWB Reservoir

Hello, just got around to starting a new watercooling build, I decided to go all out on EKWB parts. I always flush my wc parts and today I came across some weird stuff inside the reservoirs. Has anyone else seen this in their flushes or should I be worried?

It's really hard to tell. Could that be flux from your radiators that never came out when you flushed them?

Or maybe your pump is going bad and ceramic pieces are coming off the bearings?

Something is wrong for sure. I've never seen particulate like that in my loop.

That stuff came out of the radiators, the rest of the parts were very clean surprisingly.