I don't know if this is the look you are going for, but I got a bunch of small boulders from a local landscape/stone supply place for less than a buck a pound. They just look like extra large river rocks to me (meaning they are round and smooth, but not flat), and they passed the vinegar test, so I know they are aquarium safe. I got around 50 lb. rock for around $40. They won't help buffer the pH, but you can always add crushed coral, or use the cichlid buffers in the water. Cheaper alternative to Holey Rock, and you can create whatever caves and territories you want.