Peat-free bog garden

[Koen C.]

Hello all! I'm looking for some advice or ideas for my future peat-free bog garden. I will buy 1 or 2 compost units of 1 cubic meter and line them with pond liner. I like that the bog garden will be 1 meter above the ground, so it's easy to inspect, and it will have a large water volume to get through droughts. For now I have two approaches in mind to choose from:

1) Large buried buckets/pots of water upside down for volume, and inorganic medium on top as substrate for living Sphagnum. 

In this case, what substrate would be recommended? River sand? Perlite? Bims? I'm looking for a substrate in which Sphagnum will grow. Surely any of these media will have to be rinsed or soaked for a couple of weeks but i'm not sure if that's enough. Should I do testing on the pH and conductivity before selecting my medium, or are there other things to take into account, such as how course the particles are?

2) Work with 90 percent water and floating a mat on top. I would use jute, which I sometimes already use to grow Sphagnum in pots when I don't have enough volume. Has anyone done something like that before? How do I make the mat thick enough so that it is well under and well above the water line?

Before planting any carnivorous plants, I will let the Sphagnum develop for a while. They will be the indicator if the system is healthy. I choose compact slow-growing Sphagnum species in which most carnivorous plants can't get outcompeted.

Another question: how do people create drainage in a bog garden, perhaps with a PVC pipe in the middle that somehow pierces through the pond liner without causing leaks?

Any tips are welcome!