I too found some lace rock at one of the LFS
here is J'ville, FL. I asked about it and the owner told me he had been using it for years without problems...He did however tell me that if I went out on my own to find it, to make sure that it is seasoned in the sun ( like firewood I guess ) to somewhat sterilize it... ( Chose to find some on my own because of LFS
prices..Too high at $2.49 lb. ). I found some at a lanscaping retailer for $.75 lb. I bought 22 lbs of what I thought to be nice pieces and have sown no signs of dropping PH. My fish are loving it for the crevices and holes it has in it... I am going to add some LR
soon to complement its appearance....
Here is a picture of one of the pieces.. Click on the image to enlarge its detail