In many ways determining if a Japanese koi, a tropical aquarium fish, or a pond fish is healthy is a matter of first impression. That “first impression” ability however, comes with a lot of time looking at and studying fish. It should be stated that whatever the circumstance is, that has put you into possession of a new fish, ideally, ALL FISH SHOULD BE QUARANTINED BEFORE ENTERING INTO YOUR PARTICULAR AQUATIC ENVIRONMENT. Whether it be a large backyard koi pond, shubunkins, or a goldfish pond; quarantine, ideally, should be the practice. Notice I have put ideally for the quarantine piece of advice. That is because after 25+ years of fish keeping I know that the vast majority of people do not have quarantine facilities available to them. Unfortunately, most importers, and fish retailers do not quarantine their fish either. If they were to quarantine their fish before resale, you should be prepared to pay a premium for those fish, and rightfully so as the quarantine process is somewhat painstaking and requires much attention and know how, so expect to pay for that (for more on quarantine see our quarantine FAQ). When choosing new fish the average person is limited to outward appearances to make their judgment; here’s the basics on what to look for: No cuts, scrapes, abrasions, sores, or ulcers Clear bright eyes, no waxiness, no cloudiness, no bulging eyes, no damaged eyes. No raised scales, or redness to the scales. No torn fins, red streaked fins, white edged frayed fins, missing fins. No redness around the mouth, gills, or anal fin. No parasites, usually visible as white or black 1mm or smaller sized spots, or as skin protrusions. No heavy or rapid breathing, wobbly swimming, sitting on the bottom (depending on species), floating upside down, or hiding in corners. Other tips:Do not buy fish that just arrived, fish that have been around a week or more will be your better buy.Don’t buy fish on sale, there is a reason they want to sell the fish at a lower price.Check your vendor’s tanks, if there are dead fish in the tank do not buy that type of fish until they ALL look good, come back some other time.Do not buy fish that are being medicated, or that were “nursed back” to health.Try to deal with a reputable fish dealer, not the gum chewing kid who was just stocking gerbil food before you begged him to catch you some fish. Or Call FULL SERVICE AQUATICS at 908-277-6000 and have one of our aquarium specialists make your purchases for you!