Why do some catfish grow larger and quicker than their siblings?

United States
November 22, 2006 12:47pm CST
We have 14 catfish we caught at a near by lake when they were just hatched,(approx. 3/4" in size), we decided to keep them and put them in a 30gal tank. Some of our cats have grown to 8" in length while others are still very small,(1-1/2"). Why is that?
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