So, you're telling us that your markup on fish and stuff was 300% so a fish that cost you $10 you sold for $30 or are you saying you added 300% so it would be $40?
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Saltwater specialty is about 300% on livestock %130 to 200% on dry goods. Just some well know examples, clownfish wholesale at 3-5 bucks delivered and sell for 20-25 all day back then. Rare stuff gets 500% on corals typically but you have to remember stuff dies from time to time. Prior to internet competition a saltwater fish store owner could get very wealthy.