This episode must occur after The Hunted.
One of the mermaids in the tank is Silver (from the Hunted, when she overcame her fear of water), she writes on the tank wall when hanging with the math fans.
This is true, but the whole point of Rose getting knocked unconsious in this episode is so she doesn't see Jake coming to the rescure of the elders. Besides she leaves after the hunted. It's just a goof on someone's part.