Icky Output Tube (Canister Filter Related)
To make a long story short, I ran into problems with my canister filter leaking, so I had to replace all of the green rubber tubing included with my Eheim 2217 filter, with clear tubing from a local hardware store. The filter is to back to working normal now, but I've noticed something odd.
It's been running with the new tubing for close to a month now and I've noticed that some reddish brown gunk has begun to coat the insides of both the intake and output tubes. It's not thick, but it's certainly enough to see it. The tank water is in ship shape – as clear as can be.
I guess where I'm confused is why is there nasty gunk collecting in my output tube? Is that normal? Shouldn't that water be clean since it has already run through the canister?
Any input would be appreciated. Thanks!