Dick wrote in
:

I don't understand much of what you said, but I have 3 different
filters on my 5 tanks. I don't use charcoal and I removed bio wheels,
so my filtration media is a "strainer." What do you believe is
happening to the debris on the media with the water pouring past?

I just told you what happened.

Heterotrophic bacteria are breaking down the organic particles, not the
water flow or erosion.

Removing the biowheel diminishes the biological capacity of your filter to
remove the toxic ammonia produced by the action of the heterotrophic
bacteria.

Active carbon (what you call charcoal) is not really necessary.