When I moved into the new rental, there were two bowls sitting in the garden. The bowls are just on 40cm across and had a water lilly in them To me that was a bit hopeful expecting them to grow in something so small. With the bowl full the top, the ball of clay the plant is growing in is only about 3 cm below the water level. The lillies looked like they were struggling. I was not suprised given the size of the bowl and the fact that they are growing in such a small plug of clay sitting in a small bit of water. They were a bit low so I dutifully topped them up and kept making sure they stayed full. They took off and within two weeks they were both in flower.
Each flower lasts about 4 or 5 days and as it fades, the next one opens. It is a rare day when one does not have a flower open. They are thriving in that tiny space.
Recently I noticed something tiny swimming in the water. My first thought was mosquito larvae, but on closer inspection they were tadpoles. While I like frogs, they are causing a problem by burrowing into the pots with my plants, but I don't think that gives me the right to start killing them. Given the small bowl, I scooped some the tadpoles out and moved them to the other bowl. So now these tiny bowls not only house a thriving tropical waterlily, they both support a population of growing tadpoles.
Its a complete eco system in about 5 litres of water.