If you want to try this with a goldfish, consider a large enough vessel and filtration for the goldfish. Please see comments. NB as per a commentor, 5 gallons would not be enough. I urge anyone wanting to recreate this pin to consider the animal's health and well-being of utmost priority - well and truly before the aesthetic appeal of this terrarium idea. Better yet... don't try to recreate this.
Water-Loving Plants - Place a water-loving plant in a fully-enclosed mini aquarium, and you need not worry again, as Allison from Dream a Little Bigger has learned. The fish department at your local pet store should have plenty of water plants to choose from.