I am looking to add some type of big rock to my 75 gallon aquarium purely for decoration. I have done a lot of research and have found that there are many different opinions as to what is safe and what is not. My PH already tests quite high with the API kit. 7.6 - 7.9. The tank is moderately planted and has two pieces of Mopani wood with java moss and a several anubias tied to one. I have one area however that IMO would make the tank complete should there be a rock in that area. So what is safe and will not leech chemicals or raise the PH still higher? I have heard about the vinegar test but have also heard that it is not totally reliable.