if fish got as big as their habitats allowed, there would be neon tetras 100 feet long in the amason river and angels big enough to eat them in one gulp... now thats a fishI decided to test the "expert" today and asked him how big the bala and red tails get and here is his reply "They will only grow as big as your tank will allow them to grow ... +/- 12cm in a 3 foot tank"
there is some truth to that, but it is called stunting. it is unatural for the fish does not reach adult size, and it makes the fish''s life shorter and miserable because it will be sickly.