Rocks
Avoid limestone, unless you want to harden the water and get residual build-up that needs to be cleaned. If you do use limestone, you can boil it, but not for too long. Limestone already has a very high moisture content and from experience I can tell you that when used around a campfire, it can “explode” as the moisture within the stone heats up. I also wouldn’t recommended heating any shales without care (like in a pressure cooker without the weight on the valve - pressure cooker because of the heavier design and locking lid) - shale has proven more explosive encircling a campfire than limestone. Woohoo!!!
I’ve kept a natural Beryl (Aquamarine) point/section from a vein that is about 8 inches tall and 4 inches wide at its widest point, in a tank for years without any problems whatsoever. It was a rare find (had no business being where it was found in the woods near a river) and all sorts of other semi-precious and precious stones. Granite has never given me a problem. I wouldn’t suggest soft stones like soapstone though you could probably get away with calcite (marble) as long as it was clean/free of dust from origin.
Category: Philippines Internet Koi Society
