We added a new rock and two new plants to our tank as it was doing very well - and the ph has dropped to the lowest part of the 5.5-7.5 that we have been told is safe. Previously it has sat comfortably enough around 6.8. I am doing a 40% water change this evening after work. I read I can just add baking soda to the water I am adding but want to double check here before doing it and possibly harming my babies. Obviously its the rock causing this and I could remove it - but is it a forever problem if I leave it or just an acidic spike until its sat in there long enough?