What is growing in my filter??

  • We are currently upgrading MFK. thanks! -neo
I have gotten the same thing on my xp3 before. It doesn't seem to be harmful, but I have always wondered what it was too. I Haven't noticed it on any other kind of canister filter, maybe it just really shows on the xp3 blue.
 
it hasn't happened to any of my other tanks. i have even moved fish from the tank that this is in, to other tanks and still nothing.
 
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