I'm tempted to pick up a couple bags of this sand ( ), but I have three questions: 1. Is it really okay to use in freshwater? My understanding is that this is reef/beach sand and meant to help cycle tanks (I presume saltwater tanks). 2. Will it in fact not affect my pH? I'm concerned because, in short, beach sand -> coral -> higher pH. 3. Is that really sand sand? The close up picture looks like gravel. I want inert sand for (freshwater) cory cats to play in...life seems so simple until Craigslist shows up, making me all weary.