It is a heavy glass vase I got from Old Time Pottery I inverted on some concrete blocks so they could swim in from the bottom. You have to get wet to submerge the vase and turn it up under water so the vacuum created keeps the water inside. Make sure you have a heavy glass container or the weight of the water will shatter it. (court. of Rick Brown's fb page - Riverview Flower Farm Growing Florida Friendly Plants)
Wabi-kusa are balls of substrate that are covered with plants that are grown in their terrestrial form, very similar to plants that are grown hydroponically in nurseries. These substrate balls are placed directly into a small glass container with some water in and then allowed to grow naturally. Use to make islands in frog tank.