Yes, and just to clarify for pixel:
I believe both vinylman and dave are describing aspects of filtration choice that are well within the healthy averages that we read about here on TFF. vinyl is describing that fact that a well planted tank (sometimes we're talking 70% of the substrate covered with plants here - a densly planted look) will do a lot of natural biofiltration outside of what the filter is doing. In fact, the heavily planted tanks can even be somewhat vulnerable if the plants were to die, as the filter may have died off quite a bit due to lack of ammonia to feed the bacteria. But as long as everything is kept healthy in a planted tank it is a wonderful sort of environment. In a different way, dave is noting that its not that unusual to see 8x or even 10x turnover discussed, either for non-planted tanks with messy fish, or in planted tanks where the currents are kept under control and don't disturb the plantings too much.
So, like any number of other guidelines, the "5x recommended guideline" is just a sort of "starting point for consideration" thing. As vinyl mentions, media capacity is also an important difference between filters. Generally, but not always, we see a stepwise increase in media capacity as we progress from internal filter to HOB, from HOB to external cannister type, and from external canniter type to external sump. Having greater media capacity can buy the fishkeeper larger room for error when changes occur and can lengthen the time between necessary cleanings. At one extreme is mother nature, with often nearly infinite "media capacity" on a per fish basis. At the other extreme is the hobbyists limitations of money and maintenance effort for what is actually needed for their number and size of fish.
(looking back I'm not sure if this claified or muddied, lol)
~~waterdrop~~
