Folks,
Pheromones (and other metabolites) can't be easily measured, nor can their potential impact be assesed. However, they are rather large organic compounds, and the only way they can build up is if water treatment methods are not properly employed. Activated carbon, water changes and skimmers are all capable of removing organics. However, they are not so selective as to leave pheromones and other metabolites in the water to stunt the fish, while removing others differentially!
Example: trout have been grown in tubes with fresh water flowing over them. They grew to more than fill the tubes. So the size of the vessel has no direct bearing on the growth potential of the animal. Take the other extreme, where somebody has a tank and never uses carbon, never changes the water, or treats it in any way. The fish is obviously going to be stressed, and that in turn will reduce the growth rate. Our aquariums lay in between these two extremes.
Add to that mix that there are some fish that simply do not grow as well in captivity for almost everybody - humu triggers and pomacanthus angels (except blue rings) are two that come to mind.
Jay Hemdal
p.s. - the bonsai analogies here are flawed: Bonsai are not genetically produced from small trees. Some of the best bonsai are wild-collected or grafted from wild plants. The rest are grown from normal seeds and are trained to that form. As for them being hardy based on their captive longevity - not true either. Gardeners have to work with them weekly to keep them going: root trimming, leaf plucking, pest control, etc. Water them too much and they die, water them less frequently, and they die. Look at them cross-eyed, and they die. Hmmm, reminds me a lot of marine aquarium fish!<grin>.