I found the Fish of Health, in fact I have 2 of them and both are.....not so healthy. I am looking at them and it brought to mind the question 'How does this fish effect others if it is, itself, not a healthy fish?'

Having more than one does not help apparently. Fish 1 does not become more healthy if Fish 2 is in the same tank. (I know, that would be just too easy)

The Magic Fish of Health won't completely mitigate declining health caused by adverse conditions. Any fish will still lose health if it doesn't have the required level Fish Environment, if you don't feed it, or if it gets sick and you don't cure it.

However, I've discovered that having two of them in the same tank will help keep each other alive. But don't feed them (at least in level 2 environment...)

I got lucky... I hit upon the combo that produced them, followed immediately by a combo that found a canary firearrow. I was able to do a quick breed program overnight and earn enough to start the level 3 researching...

Exactly. An snooper supporting another, and that supporting the other is the magical way to get L3 fishes grow enough without buying the best environment. If feeding them lowers the energy, and the snoopers are in 0 of health, they die: the magic is not forever! So if you get this combo, buy as quickly as possible L3 fish environment research.