Its not to do with the decoration, it is to do with the fish feeling insecure as it does not have the protection of the shoal around it. It is a problem when buying a fish to add to a shoal - and in this instance my view stands that it is just going to be too stressed in qt, which will weaken the immune.
I also think that qt is a stressful experiance for fish, I know it has many advantages, but there are nearly equal disadvantages. I prefer to get my fish settled down ASAP rather than dither aroud moving them here there and everywhere. I know many people have had disasterous conciquences of skipping qt, but its a risk you take. if fish were qt in the shop (like most good shops should) then there is no point in repeating the process again I feel.
I also think that qt is a stressful experiance for fish, I know it has many advantages, but there are nearly equal disadvantages. I prefer to get my fish settled down ASAP rather than dither aroud moving them here there and everywhere. I know many people have had disasterous conciquences of skipping qt, but its a risk you take. if fish were qt in the shop (like most good shops should) then there is no point in repeating the process again I feel.