Terrarium pond

Question:
I want to make a little pond in my terrarium, and my terrarium is covered all in substrate,?
How can I make a little pond without it mixing with the substrate, my tank is 20g Wide.
Answer:
It depends on how big you want the pond to be. If it is to be small, you can just sink a jar lid in. If you want it bigger, use a flat plastic or glass saucer. I have used the saucers that go under flower pots and found that they work well. I put bits of flat stones around the edges, so it all looks natural.