We can agree to disagree. I'm certain your fish are healthy and happy. Nobody here suggested that fish be kept in a tiny tank, under 5 gallons. I was merely indicating what my search results offered.
For a 12 inch fish, I do doubt that a 5 gallon tank would be adequate to hold more than it's tail. The generally accepted rule of thumb is 1 inch of fish per gallon of water. Any less and the fish may very well starve for oxygen or suffer from disease. In this case, yes, a 55-60 gallon tank would be "just" sufficient. Some more demanding fish may require more than what 1 gallon can supply them, and in this case, 1 inch per 2-3 gallons may be called for.
While we may disagree with what others post, do the research yourself if you have indepth questions.
Sneakypete, I'm sorry if I hurt your feelings, as the tone of your posts suggest. I am a huge stickler for acurate facts, and I will spend HOURS researching one angle in order to find accurate information. The site you mentioned sounds like a good resource, and one I may look into for future questions.
I'm firm - but fair. Mind the rules and enjoy your stay.
According to the Humane Society of the United States:
There are an estimated 3-4 million dogs and cats euthanized each year in the US alone! PLEASE - spay and/or neuter your pets!