Hey guys, so I am having problems with keeping my pH up. I think the river rock or something in the system is acidic... I am pulling the fish out and doing a water change with tap water that has been dechlorinated with vitamin C and has been left out for 24 hours. I hope this water change helps with the pH, but have a feeling it will fall again. Can anyone give me an idea on how much shellrock or oyster shells I will need to make a perm. buffer in the system? I ordered the parts to make a sump tank connected to the FT to allow more water in the system and what would house the oyster shells.