I just wanted to post this little note about how important buffers are when you have soft water like I do.
I just tested the perams in my QT tank. I hadn't added buffer to it (since it's empty) and was shocked to see that in just a week, the pH was nearly down to 6.0!! Out of the tap it's about 7.0.
I ran out and tested my main tank straight away. I always buffer it using buff-it-up, but I was worried. But, my tank was at a healthy 7.3. PHEW!!!
So don't underestimate how quickly your pH can drop in unbuffered water.