Alkalinity???

Well, 7.8-8.4 is a rather larger difference first. Second, don't go messing around with your pH if you already have the fish. They are used to it and changing it will probably hurt more than help. The kH is high too, which is going to make it rather difficult anyway.

You really should not change your water chemistry if your only goal is to keep the fish; it take diligence (sp?) and understanding how the chemistry works/ why you are changing it.

HTH

Well, can you give us a more accurate reading on your pH? It's a little too broad for us to even tell if you need to change your water, which I don't think you are going to have to or should if you're just starting out.