[pogodzib]

Some people have used lava rock for years in reef tanks with no ill effects. Other people have tried using lava rock and killed off their entire tanks. It's a crap shoot and will depend on the chemical impurities in the rock that will determine if it works or not. Unfortunately, it can be tough to know until it is placed in your tank and used for a little while. By then, it could be too late. Getting lava rock from a pet store would be safer than getting it from a landscaping store since the source of the rock is probably coming from a place that has been tested for impurities and rocks from the same site has been used in aquariums previously. The lava rock at landscaping stores may be coming from a different location that has different types or higher levels of impurities.