DO NOT LISTEN TO ANY NOOB PEOPLE! True a captive bred fish will grow slightly smaller than in the wild but not by much at all. For instance a wild Managuense has the ability to grow 22" now a captive bred fish will grow slightly smaller only because the parents and off spring are altering to more suitable conditions for the next generations to come. Now that doesn't mean a Manguense will grow 12" because that ain't friggin happenin it will grow to 18" when about 15 years old. Never ever buy fish thinking oh it will grow to the size of the tank. This is called stunting. What stunting is, is when the skeleton of the fish begins to slow down in growth and eventually stop, but (and a MAJOR but) The internal organs will not stop growing inside. This will cause the fish to suffer severe spine problems, bleeding from the sides of scales in serious cases, eye bulge, and respitory problems. Now not only does this happen but if you don't keep up on your WC's because now you have a big fish in a little tank the nitrates are going to go off the roof. Now when they get to high the fish will try and protect itself from the harmful enviroment by building up a thicker slime coat in order to control the water quality from hurting it. A thick slime coat also makes the fish suffer in great ways. It will now be more susceptable to disease as with stunting too. It's just not a good idea and don't try it.