I went to a local water garden place to get expanded shale, but due to the tiny size of it (the big pieces were about 1/4"), I couldn't use it.  The salesman assured me that their pea gravel was pH neutral (I asked him 3 or 4 times during the conversation).  So, he talked me into it, but we discovered that they were out of stock.  He said that it would be in the next day.  Now, a week later, afte…