I have a 135 freshwater aquarium with about 30 different tetras. I want to put some discus in there and have been trying to get the ph down with no luck.. I put in some neutral regulator to get it to 7 and it was still at 7.8. So, I started using the discus buffer and now, after 3 treatments, its finally down to 7. I've had aquariums for a very long time and I've never had this kind of problem with the ph before. The gravel is your standard quartz from petsmart, and I don't have any rocks in there. Any help or input would be appreciated. Thanks..