I understand where your coming from, I can see why one would favor the more expensive fish over another, believe me
I am merely trying to make it a little clearer as to why its rather unnecessary, inaccurate, and, in my personal view, a bit cruel. It seems I must not be explaining it right....
I stress again, if you know your fish well then you know the 'weakest link' in your tank....but even then it could be a totally other fish that gets something. Its chance with disease really, you may have more sensitive fish that are fine yet loose a hardier fish to dropsy. What I'm trying to say is, there really is no sort of 'indicator fish' for disease. And what I mean by stressing the test kit is that if you know your levels then you should know your water quality, there really is no point in getting a fish to tell you this as that is, I would believe, far more unreliable then even a test strip. There is a high chance the fish will not tell you when your wanter is bad, where a test kit will no matter what. Your "Canary" fish may even thrive while your others dye out, it really depends.
Originally Posted by nomel
And I know that good water conditions are the best way to help ensure that nothing bad happens to any of them...but what's wrong with "over testing" with a biological tester, in addition to partial water changes and frequent "water quality" checks? (in quotes, because if I went out and tested random puddles of water, in search for one to drink, using an aquarium test kit, I'd surely get sick or poisoned...they're limited in their scope...I'd like an ideal indicator...which would be one that indicates if life is sustainable).
.....I'm unsure where your going with this. Of course going out to test puddles with an aquarium test kit to try and find one to drink would be ridiculous, humans are far different creatures from fish and have far different needs. A good liquid test kit like the API brand isn't 'limited in its scope'. It will tell you what you need to know and if your water is safe for your fish. You can never have a definite, ideal, 100% indicator if something is going wrong but a test kit will tell you more then any one fish or invert. Theres just that risk with fish keeping, you can never know for sure.
End decision is up to you of course, I'm only trying to explain things a little better.