- Jun 6, 2012
- Reaction score
We are digging a 3 ft. deep pond with an 18 inch shelf around it. We plan to slope or tilt the sides back so we can stack rocks up the sides on the shelf. Should we use concrete to secure the rocks (if so what kind of crete would be safe for koi?) or buy spray foam to secure them? We are using a flexible EPDM liner.