I was just trying to use a general rule.
An example is, she has had a Niger, Picasso and very large Engineer Goby in the same tank for months.
She does have the fish tanks on the same system, the inverts are separate and so is the coral tank.
In this case, the fish have not been sick, have been active and I have seen them eat. Would QT be vital to "establisshed" fish, like this situation?
I can understand if she has a new batch in, which I would wait a few weeks, to observe, before purchasing anything. I am just wondering, I plan on QT'ing anyway, since I only have sand in my 125G right now...waiting on the base rock.