Keeping pH higher and stable

Hello all,
I have had a small, 36 gallon reef tank for just over a year now. Everything is fine, but no matter how hard I try, I can NEVER keep my pH at the right level, and stable. I use Kent Marine Superbuffer dKH. I buffer all water that goes into the system, and I top off about a gallon a day, buffered. I have my LFS test my water about once a week and they always tell me to buffer for a couple days, so I do, but then the next week it is down to around 7.7-7.8!!! I can never keep it higher or stable. I am going to start a seahorse tank, but I want to make sure that I can keep my pH at acceptable levels before I get any for a new tank. I was looking for some advice on keeping my pH at acceptable levels and stable. Also, what products that you use to buffer your water. Also, anyone who uses Kent Marine Superbuffer dKH, please tell me how you use this product!!!!!!
Marc