****big fish question***?

ok so i am getting a 300 gallon tank and a red tailed catfish but i heard they need more but here a href="http://www.liveaquaria.com/product/prod_display.cfm?c=830+1163+929&pcatid=929" rel="nofollow"http://www.liveaquaria.com/product/prod_…/a it says 300 so is that right or do i need bigger tank?