The point is, one would know if fish are happy in their environment by their general health and life span. That's the only way to know for sure you're doing the right thing...If you're changing fish often, change your habits..
The problem is, when you browse the discus forums, knowing that majority of so called experienced discus keepers use bare bottom tanks, it does raise your eyebrows why the forums are saturated with topics on sick discus....Don't get me wrong, I love reading the topics because the knowledge on diseases is great in there.
But there's a big connection between stress and disease...Fish diseases and regular deaths are a sign of severe or/and consistent stress...I don't know if its more difficult or easier for the fish care taker to keep fish in bare bottom tanks in that case. But hey, they say it works better for discus.....I think the problem with keeping discus in decorated/planted tanks is the amount of food one needs to feed them if you want to grow them big... Such food and amounts will wreak havoc in any tank early or later....So for growing up fish I understand why its done that way...But adult fish should be in planted or biotope tanks with all the cover necessary...
Plus it won't hurt a thing to put a few potted plants and a driftwood for some cover in any bare tank...I think its laziness and stubbornness...Fine layer of sand to prevent bacterial growth won't hurt either. No one can convince me you can't siphon it well....Majority of their home tanks by my observation are majorly under-filtered.... Add to that the high temperatures and slow moving waters lacking oxygen....Everything in those types of set ups would shorten the lives of majority of fish...
In discus nurseries, there's a subtle difference in how fish are kept. The filtration is massive. I can't remember which one I watched lately, but they had massive trickle filters under the tanks that they Didn't clean at all often because the enormous sponges were on top and the debris settled on the bottom where it gets flushed...The water changes are automatic, no wiping and messing with the tank with the fish inside. Its drain and fill...
In a home aquaria it becomes different with the amount of food those fish are being fed, wiping everything like a lunatic, washing the clogged media daily, they are disturbing the bacs non-stop...leading to immature filtration consistently..
And they often deal with lingering ammonia and nitrite as a result....Then dump meds to remedy the problem....led by the panic and fear of losing their expensive fish...
Some don't even bother with filtration because of the large daily water changes...I couldn't even keep 3 shrimp in an immature fish tank. even with water changes...The test was barely reading 0.25 ammo and the shrimp had frozen on their chosen spots and not moving...
Rant over....