Haha. I'm afraid I will do that in the future haha. But, I hope not. 16 cactus is enough. I guess, but found some beautiful one in a cactus expo. But, it's very expensive. Very very expensive. I will just wait until my birthday comes so I can wish to have it. Hahaha. I just put the lava on top. The rest below it is mixed of soil and small stones.