Sounds like good observation and experimentation on your part. Be sure to check this cloth frequently - any sort of cloth that forms a fine screen on filter water flow will begin to collect particles and bacteria and at some point become "stiff" feeling. This could eventually back up your filter. I'm not suggesting not to do it but just to keep your observations of it frequent enough to avoid problems.
Current and circulation in an aquarium can be a surprisingly complicated subject if you get in to it. Each animal and plant species evolved in a habitat or range of habitats that will have had particular characteristics and some of them were likely quite different from the little glass box worlds we provide.
Of course all sorts of needs are being met by tank circulation: the aquarist is looking for a certain flow rate that aids in the overall maintenance process by collecting some of the debris on an ongoing basis and allowing it to break down and feed the filter bacterial populations. The surface is being disturbed to aid in the alteration of gas exchanges such as oxygen and carbon dioxide. The minerals and nutrients for use by both plants and fish are being distributed to some level of evenness by the water movement. The dozens of algae species looking for homes are seeking out the best spots for their existence. All sorts of things.
Fish themselves need exercise of course, just like any other animal species and having higher flow spots in a tank can help provide this, especially in lieu of large swimming spaces (or in addition to that.) As long as there are also quiet spots in the tank, the fish can obtain what they need in a natural way but as an aquarist a typical goal is for the circulation to not encourage your fish to rest in a non-visible place relative to the observers. It can take plenty of time and experimentation to get this just the way you want!
Plants too are quite dependent on circulation being right, perhaps even more so than their more mobile tank inhabitants. Study the planted tank world and you'll quickly find that somewhat higher overall flow is often considered a desirable thing! Anyway, it's a big topic. No one should be afraid to experiment.
~~waterdrop~~
