lol.... by the time you complete the research, the nice clams are all gone already. I have seen other clams in nanos so should be ok.
My thoughts are that yeah you need to know roughly certain things before you embark - can clams be kept in a reef tank, what do you feed, what lighting you need, what elements are crucial to them.
Whereas for more detailed stuff like how to tell they are happy, are they growing etc etc, then can learn as you go.
Learning is an ongoing process throughout this hobby anyway.
My concern is usually not whether we are researching IN DETAIL before we buy or after. (like I mention above, you need to know in advance if it is suitable for your tank though)
It is more of whether the buyer is buying on impulse, does he know the consequences or if he is dedicated enough to see that the livestock requirements are met adequately.
In this particular case, whether he knows that he will need to dose liquid food, calcium on a regular basis.
Just sharing my philosophy.