They do,if they live long enough.The LFS people are going to sell whatever they can get that will make money for them.My problem is when they misinform or mislead customers in order to make such sales.Arapaima are usually not cheap to the casual aquarist though and it is really the responsibility of the buyer to know what he is buying and whether or not he can house it.
haha. That was the first thing that popped into my head when I saw the title. Never seen pics of baby arapaimas before, so thought the pic was some sort of catfish.