Fish species that have evolved to utilize atmospheric oxygen have done so because the water they inhabit in nature is oxygen deficient...which typically means relatively warm water that is stagnant and lacking in current. I don't think it's reasonable to expect them to "re-evolve" on a moment's notice just because we want our tanks to be easier to keep clean.
On top of that, a degree of current that is easily handled by a larger fish...like an adult arowana...can just as easily become a bit overwhelming for very small specimens of the same species. And, of course, many or even most species that live in water that appears to be flowing very quickly, actually spend almost all of their time in the lee of large boulders, in slack backwaters and eddies, and other protected areas. Trout fishermen spend all their time looking for prime spots to present their lures to their quarry. Do they typically cast into the boiling, roiling rapids? Nope, almost never; instead, they move from pool to pool, and look for current breaks and other obstructions that create quieter resting and ambush points for the fish.
Don't believe it? Think that all your fish will be happiest living in water that looks like the Heavy Dirt cycle of an industrial washing machine? Lots of aquarists feel that way; more has just got to be better, right? Well...no need to overthink it. Just watch the fish. You have already seen that your fish seems to prefer less current.
Hmmm...what to do...what to do...?
Understood.... Wave maker will be used to periodically stir up the gunk at the bottom other than that it will be off. It takes place of a vacuum in my case.
