I recently purchased 2 ton of river rock from a local stone supplier at $22/ton. But I was concerned about the Intex liner, since not all the rocks are perfectly round. I found some rubber pvc pipe insulation at Lowe's for $6.68 and my 24' pool took about 7 of them, which I cut in half. The rock in enclosed with red bricks. The measured distance around my pool was 75 feet. Thought about pool noodles but they fall apart too easy, besides the black rubber looks better! Here's the link to what I used:
Here's how it looks: https://www.flickr.com/photos/956913...in/photostream
Hope this helps!