If you have integrity and show some care in your selection process you can be in business without selling the questionable animals.
In fact if I started stocking unsuitable species I'd probably go out of business because they simply don't live long enough to make it through my turnover before dying either from shipping stress or starvation or whatever makes them unsuitable.
If you look at my livestock guarentee policy:
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For livestock which has died, the specimen must be returned within 48 hours along with a water sample for testing. A refund may not be given if your water quality tests poor. While we will make every effort to ensure the long term health of your purchase, we can not be responsible for losses due to aggressive tank mates, long periods in transit to your home, etc. Due to their sensitive nature and demanding requirements, we can not give refunds for small polyp stony corals.
99% of my SPS is captive bred but since they sometimes will melt for no reason we will not guarentee them and to be honest I don't think it has ever been an issue. Long transit periods being anything over an hour. No we don't ship livestock because of the stresses involved and because it's just too much of a hassle.
If you look at my Livestock Availability you will see what my instore labeling looks like.
For fish check out:
Angelfishfor corals check out:
LPS Corals We do classify animals for beginner, intermediate, expert and surprisingly a good percentage of the time this works quite well with the aquarist self regulating their purchases to match their own perceived skill level. If you take a look at the label for Tubastrea I would say this is a coral that is quite difficult to keep if you aren't dedicated but I don't think it should be restricted from collection as long as the LFS does their job of prescreening the purchaser.