Aquascaper
Fish Aficionado
Another one for the pin board
Good info mate
Good info mate

Ok could a mod edit in that excelent point please and creditInchworm said:Excellent point, SirMinion![]()
This would be especially likely to happen to volcanic rock that has been washed and/or soaked before putting in the oven.I've seen this happen when lava rock was used to circle a campfire, and this was in the Arizona desert where it hadn't rained for quite some time.