In the issue of water flow, we must keep in mind the observation Oliver makes in this video. There is a current in the channel (current, not whirlpool) such that it will carry a leaf downstream. But along the margins the dried leaves remain stationary. This means that the fish can actively swim against the current, but they have the ability to get out of the current. The main issue with an aquarium is finding this balance of both features. In a large tank, meaning a 4-foot or larger, this is easier to do, I;ve done it. But in a tank that is less in length, it is not easy. I did it in my 40g cory tank. At 3 feet in length, the internal filter in the upper right rear corner was directed down the length of the back wall, hit the far end wall and headed back, but the return journey down the front of the tank was very minimal; plant leaves did not move in this soft current. My pandas liked the stronger current, but many of the other species primarily avoided it. Fish fighting a current cannot rest as well, and this wears them out because the water movement is 24/7.
Another observation on the light sand...this is normal, buff or tan colour sand, Many species of cories--C. panda, adolfoi and related species, axelrodi, etc.--have the identical body colour so they blend in, as Gary noted above. But most of these habitats do not have direct sunlight, but rather overhanging forest canopy. The sand does not therefore reflect bright light. In many of our aquaria, we have overhead light, and this without question is very stressful on forest fish. This is why white sand is verboten, it is far too reflective. Black sand goes the opposite direction, and these same cories have stress from this too.
Life in an aquarium has to be as reasonably close to life in the habitat with respect to the physical environment. This is programmed into the species, and it is what they "expect."