If this is double posted I apologize. I have a 25gal tank approximately 5mo old. My fish are dying. Ph6.0, NH3 0 , nitrite 0, N03 5. I have been doing partial water changes almost daily. My ph used to be in 7.0 range. I do have some plants (unknown what kind). I just want to keep guppies but if I keep killing them I will take down tank as I am frustrated!!! I have read crushed coral can help buffer tank to prevent Ph from dropping. Any advice welcome.