Freshwater

Just because a fish has been medicated does not mean that it is completely
well again. Let your eye be the best judge; carefully inspect any fish for signs
of disease, such as torn or clamped fins, white spots or growths, or irregularly
shaped bodies.
Start simply
If you are new to the hobby, never buy hard-to-maintain and feed species of
fish such as piranhas, pacus, or oscars.. Fish that have special dietary
requirements may be too much to handle in the beginning when you are still
trying to get the hang of how your equipment works. Wait until you are completely
familiar with your system before trying your luck with the harder-tomaintain
species of tropical fish.
Go with what you know
Do not buy fish that are completely unfamiliar. Just because you are browsing
the store and happen to a see a cool-looking fish doesn’t mean you should
take it home. Some species can be very difficult to feed and require strict
water conditions to survive. Leave them in the hands of the pros to avoid
heartache. Fish marked as “hardy” (guppies, platys, and swordfish, for example)
are easier to keep for beginners. If you do want to try a more difficult to
keep species, make sure you do your research (via Internet sites dedicated to
particular species and talking to experienced hobbyists and pet store personnel
who keep that type of fish) before buying so that you know exactly what
that fish will require to flourish.
Look for signs of good health
Chapter 9: Purchasing Your Fish
You can look at several physical characteristics to determine whether your
fish are in good health. There is never a guarantee of complete success, but if
you follow these rules, you increase your chances of getting a healthy specimen.
Look for the following:
Body color is rich, not faded or dull. The color should be complete and
not missing in any areas (unless it is typical for the species).
There are no open sores, visible ulcers, boils, or obvious skin problems,
such as peeling scales or blemishes.
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