Originally Posted by candymancan
I thought lava rock was inert .. I have used red lava rock in my fresh water tanks for decades never had any issue
Lava rock can conatins metals. Therefore its already a risk to place it into your Marine aquarium. There is no way of knowing what it could potentially do. unless you have a way of testing wether it will leech and or has metals in it then i wouldn't risk it, especially with inverts or corals. Plus some people have said it tends to break down over time and crumble. This is just my research on other forum in a matter of a few minutes. There is plenty of reading material out there. Its just how bad do you want it in your tank? Enough to risk your livestock and the rest of you rock and sand becoming contaminated?