Just another thought - In a 8-month-old low-tech tank (25g) I had a huge mass of moss recently. Several times a week i would take a chopstick and bat it around a bit, and huge amounts of brown "stuff" would float off of it. I had an AC70 for many months beforehand, so total flow was not an issue. I recently both trimmed out most of the moss and added a mass of polyfil on top of the two AC sponges i'd had.
Now, there's very little brown gunk that i can bat off of leaves, and the polyfil is incredibly gunked up.
Based on my experience, thin-leaved plants collect garbage, and finer mech filtration catches it. If you don't want to trim, consider adding fine-mesh mechanical filtration to whatever you've got.