I have heard conflicting information about the keeping of Royal Clown Knives, Clown Knives, and Gold/Albino Clown Knives. I have a 55ga set-up with 5 Parrots and 5 Knives (2 Royals, 2 Clown, and 1 Gold/Albino). I have been told that I cannot have more than one Knife (I prefer the featherbacks...