Foam in sump filter?

[Jamesabbott418]

I have a sump filter setup for my 125 with koi in it,
I have a fine foam type filter that I cut to fit in my aquarium, underneath that is my bio balls then I have k1 media in the next section on the sump.... I have been using the foam for about 6 months cleaning it and or replacing as needed but it seems that my bio ball are always clean and my k1 media has not changed color as the description said it would after being covered with bacteria or ripe I guess you could say...
Is the foam causing the rest of my sump to be useless? Would it be better to not even use the foam

[kenny69]

I assume the foam is the mechanical filter? I'd leave it.

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