I hear you but I also see that you’re wrong. So many keeping well established planted tanks with discus. These are discus keepers who’ve figured out how to do it. Yes many beginners attempt it and fail. But many beginners start bare bottom and fail. Another member hear has a 55g tank with one discus tons of algae and crystal clear water that he tops off regularly. Bought the fish at 2 inch. It’s a full 6” now and looks great. 5yrs old. IMG_8573.jpg.
I’ve got 4” discus that I bought from a sponsor. Came 4” and never grew. In my 180 where other fish have grown well over 6”. I’ve also bought 3 6” discus from a sponsor that came in beautiful. But only one has kept its color and one just wasted away. These were kept in a bare bottom tank. No other discus showed any sign of sickness.
Now the fully planted tank I’ve got pictured. Those discus were all 2”. A mixture of Hans and local. That tank started with young discus and small young plants. All grew together.IMG_3363.jpg most hit the 6” size. Some were stunted just like I’ve had stunted in bare bottom tanks. Stunting just happens. Some cull them. Also this tank got 2 50% waterchanges weekly. These were gravel vacuuming water changes. Funny thing is plants did great! People who don’t want to change water are just that. Some are successful. Some swear you don’t need to change water and show there results on a regular basis. Seems there are other approaches that work.