Hell, the way I'd look at it is that if he couldn't be bothered to give a shi... then why on earth sould he expect his (lack of) customers to? Businesses like that are simply asking to go bust beceasue of their inherent ingorant arrogancy.
Supply and demand. If you have a potential CUSTOMER with MONEY in your SHOP, then it does not take Sherlock bloody Holmes to conculde the SUPPLY bit!
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Andy
However, with supply and demand you may have hit the nail on the head. If the OP's fish store has survived for 35 years selling stock community fish and plastic plants, why would he want to change a winning formula?
Essentially, he has had customers coming in with demands for community fish such as neons and guppies for years, so he stocks those fish that he knows he has a demand for.
Remember that he runs a business, not an attempt to become well known on a fish forum for stocking rare fish. The fact he has been in business for 35 years would appear to indicate he actually has a pretty good grasp on what his customers want.
You seem to be upset that he isn't stocking what you (one customer) wants because he is catering to all the other customers who do want those items he stocks.