I use playsand in 4 of my tanks and I havn't noticed any problems. Some people do advocate that you should stir the sand as it has been reported that gas bubbles can build up as play sand compacts easily. The stiring releases these bubbles before they can build up to dangerous levels. How far this is true hasn't been 100% confirmed, so I just stir the sand anyway, better safe than sorry. In anycase the bubbles shouldn't scare you off using sand, I personally think it looks better than gravel.