Lava Rock?

[Jc1119]

Some lava rock is safe and some isn't. It depends upon the composition of the lava rock. Some lava rock contains heavy metals which can leach into the water and kill your fish and corals. Most of the rock used in saltwater tanks is porous and composed of limestone. The porosity encourages bacterial growth and the limestone helps maintain the pH and provides needed minerals for your corals.

Exactly. Metals in a reef system are generally not a good thing. Limestone, Fieldstone or base rock is best and really not that expensive, or at least not compared to what it would cost to restock your tank.