LOL

might be appropriate!
or you could ask him why he didn;t declare his stolen biosamples, or from which box of crackerjacks he got any qualifications he claims to have as a "researcher", or which University he is affiliated with, or for any peer reviewed work of his own that he has ever had published.

You can also count how many times he mentions that you should buy some book of his or uses the first person personal pronoun LOL
$10 is a decent price for a good laugh, but don;t you think that perhaps engaging criminals like him actually brings the particular aquarium club into disrepute and further encourages his criminal activities?