What is this foam like stuff in my canister?

I was cleaning my canister filter yesterday and noticed the trays and the area around the impeller had a whitish foam in random spots that was stuck to the plastic. It was a solid, almost like the consistency of those egg crate foam cushions people put under sleeping bags. Also, it was adhered to the plastic semi well, rinsing it alone didn't remove most of it, but a sponge took it off easily.
Any experienced this before, or have any suggestions on what it could be?

Thanks

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A better description of its consistency might be to say it is cotton-like.

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The little research I've been able to do suggests it could possibly be some type of fungus, but I'm surprised no one else had an opinion on it

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