I'm thinking about using this natural product to lower my ph, which is currently at 7.6. I keep angels, plecos and recently discus. I think a lower ph would be better for them. Anyway, I know Indian Almond Leaves lower ph in tank naturally, but how would I go about using it? How often does it need to be changed and how much would I use? Tank sizes are 72 gal and 55 gal.