Young smaller fish of the geo. species should be housed with sand. As they grow larger fine gravel can be used. The fish can live without this however as you mentioned they will most likely become stressed and annoyed. These species have a very interesting way of feeding .. a behavior that keeps them active all the time. They way they are able to filter still amazes me for some reason.
I'd say you should get an oscar. But only one. He will grow on you( both literally and as a figure of speech) htey make great pets, when they trust you you can even pet them