Well, the first thing you should advise them is to remove the fish and anemone and anything alive from the tank until it is fully cycled. SW
fish cannot tolerate the ammonia of a cycle like some FW
fish can, this person is definitely going to lose the anemone (not recommended for tanks under a year old) and likely to lose the fish. It is easier, cheaper and more humane to cycle the tank with a piece of raw cocktail shrimp from the grocers seafood counter.