Once upon a time, most of us actually went into a Local Fish Shop (LFS) to pick out our fish in person. So, this write-up is geared more towards those who still pick out their fish as opposed to just ordering online. Sometimes ordering livestock online is like getting a box of chocolates... 
UNLESS you are buying (shameless plug coming) from a HF approved vendor that only sells WYSIWYG quarantined, conditioned fish: HumbleFish Forum
So, you walk into your favorite LFS and see all these amazing fish. :love: What should you be looking for?
Ask what salinity the fish is being kept in at the LFS, but verify this yourself by sticking a small needle through the bag (just above the water line), take a water sample using a pipette and then quickly close the tiny hole using a piece of scotch tape. If SG of the bag water is within 0.001 (+/-) of the receiving tank, you can just float & release after 30-45 minutes (to temperature acclimate). Any salinity outside of that range will require a drip acclimation as outlined in the article above.
Using a quarantine tank for your new fish purchase(s) is HIGHLY RECOMMENDED: How To - Quarantine
One of the nice things about using a Quarantine Tank, in conjunction with buying from a LFS, is you can set water temp & salinity to match whatever the store normally keeps their fish in. By constantly maintaining these parameters in your QT, you are always ready to buy a new fish! You can then raise salinity (if needed) to match your display tank for when the fish is out of quarantine. I typically accomplish this by topping off with saltwater instead of RODI. :Thumbs_up_green:
Whether to prophylactically treat or just passively observe in QT is a personal choice, and is discussed further in this article: Chemoprophylaxis vs. Observational Quarantine
UNLESS you are buying (shameless plug coming) from a HF approved vendor that only sells WYSIWYG quarantined, conditioned fish: HumbleFish ForumSo, you walk into your favorite LFS and see all these amazing fish. :love: What should you be looking for?
- Bright colors - A pale fish could just be an indication of stress, but it can also be a sign of disease. Not worth the risk.
- Fins & spines are on FULL DISPLAY - Clamped fins are sometimes also just a stress indicator... but can also be a symptom of disease. Again, not worth the risk finding out which it actually is.
- BIG PLUS if the fish is out swimming or is actually being sociable with you - This is sometimes an unrealistic expectation, as most fish at a LFS tend to hide. That behavior is pretty normal because the fish is still trying to figure out its territory and has not yet adjusted to aquarium life. But if you do see a fish you like swimming out in the open or even interacting with you through the glass, that is a very good sign!
- Avoid fish with visible physical symptoms of disease or injury - White dots or splotches, stringy mucous coming off the fish, red sores or streaks, fin erosion or body damage are all bad signs. The fish should look flawless! Discoloration sometimes is just due to a fish's stress pattern, but you should observe the fish for a while to see if coloration returns to normal.
- Avoid fish with behavioral signs of disease - Heavy breathing, scratching/flashing, head twitching, yawning, erratic swimming behavior. These last two are somewhat unique to Marine Velvet Disease and fish with these symptoms should be especially avoided: Swimming into the flow of a wavemaker or powerhead, and fish which seem to be purposely staying out of the light (Velvet causes fish to be sensitive to light).
- DO NOT buy any fish which shares water with a diseased fish - Keep in mind that many Local Fish Shops have some or all of their tanks plumbed together with a common sump. Sometimes there is a UV sterilizer plumbed into the common return line, but you still have to consider three things: a) Is the flow rate slow enough to eliminate pathogens? b) Cross contamination via nets and wet hands c) Aerosol transmission.
- Ask the LFS if their fish are being kept in copper or some other medication(s) - This is not necessarily a dealbreaker, but just know that fish kept in subtherapeutic copper will oftentimes look/act better than they actually are. The low copper is just keeping the parasites at a sublethal concentration. Once the fish is removed from this environment and placed in non-medicated water, many times the parasites are able to then multiple and overwhelm a fish's natural immune system. And spread disease throughout the entire tank. One thing you can do is find out (and double-check yourself) what copper level the fish are being kept in and then set your Quarantine Tank (QT) to match. You can then raise the copper up to full therapeutic, and finish the job that the LFS began for you.
- Ask to see the fish eat - I cannot stress the importance of this enough! DO NOT buy a fish unless you see that it is eating. If a LFS refuses to feed the fish for you, either walk out or ask when is feeding time so you can return later. Do not leave that shop without whatever food you saw the fish eat! An eating fish gives you at least a fighting chance with it. (y)
- It's never a bad idea to study the fish you want to buy - Make daily visits to the LFS (if possible) to see how your potential fish purchase is doing. Of course, you risk that the fish might be purchased by someone else but another fish you like even better may come along instead. Be patient.
- Use a magnifying glass - IF you can get close enough to a fish for this, use a magnifying glass (many smart phones have this feature built-in) to more closely examine your potential fish purchase. You'll be amazed what you can sometimes see under a magnifying glass that your eyes completely missed!
Ask what salinity the fish is being kept in at the LFS, but verify this yourself by sticking a small needle through the bag (just above the water line), take a water sample using a pipette and then quickly close the tiny hole using a piece of scotch tape. If SG of the bag water is within 0.001 (+/-) of the receiving tank, you can just float & release after 30-45 minutes (to temperature acclimate). Any salinity outside of that range will require a drip acclimation as outlined in the article above.
Using a quarantine tank for your new fish purchase(s) is HIGHLY RECOMMENDED: How To - Quarantine
One of the nice things about using a Quarantine Tank, in conjunction with buying from a LFS, is you can set water temp & salinity to match whatever the store normally keeps their fish in. By constantly maintaining these parameters in your QT, you are always ready to buy a new fish! You can then raise salinity (if needed) to match your display tank for when the fish is out of quarantine. I typically accomplish this by topping off with saltwater instead of RODI. :Thumbs_up_green:
Whether to prophylactically treat or just passively observe in QT is a personal choice, and is discussed further in this article: Chemoprophylaxis vs. Observational Quarantine
