Substrate for plants with darts

[MichielB]

That depends on the plants you want to grow. There's little to no nutrition in the bottom and if I'm not mistaking sphaghnum moss will give a slightly acidic soil.

Choose your plants accordingly and depending on the moisture level.

[cobe]

I use a layer of clay balls on the base then i add orchid compost (you can buy it form most garden stores) as a top layer. Ive used it for many years with great results.