my water out of the tap is 6.6PH or lower and my 75 gallon is sitting at 6 right now. I use alkaline buffer by seachem on water changes but I am looking for a way to passively buffer. I have an Eheim 2028, an ac70, a large sponge filter in this heavily planted and hardscaped tank with ada aquasoil as the substrate (yes I know it lowers it but I thought it was meant to buffer it to 6.5 ?? ), I currently has only 1 betta and about 24 red cherry shrimp in it, I'm sitting about 30-40 ppm nitrate and near 0 ammonia and nitrite. I was told to use egg shells, crushed coral or shells of oysters to buffer but I don't know how much to use. Thanks for helping this new aquarist out!