It may be wrong that they aren't doing what is necessary to keep the corals alive, but what they are doing is not wrong from a business standpoint.
To the untrained eye it may appear pretty dumb that they would rather see it die than give it away for almost nothing, but in a business sense. When running a business you have the ability to write off losses on your taxes. If they sold it to you for almost nothing they would lose money, if they write it off on taxes they get the full value as a deduction. Most, if not all, of these stores have nothing but their bottom line in mind. They are running a business, charity does not put food on the table.