Royals get pretty big and they like to move around 72 by 24 is min. for a full grown one or they just look ridicoulsly large in a smaller tank. They get twelve inches long(min), but you also have to realize that they get almost 6 inches wide. I had a full grown one in a 48 by 18 and it did not have enough room. Plus they add a huge amount pf waste to the system and eat huge amounts of cucumber blood worms when they reach that size.
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