I found Debra Wink's pineapple starter writings (which appear to be the same recipe you're using), and inspired by her findings, I started my own trials. Now on day nine, the results are interesting. I have three batches going: one with distilled water and a blend of 50/50 whole wheat/bread flour; one with tap water and the same 50/50 flour blend, and another starter with pineapple juice and whole wheat flour that I'm now feeding with only bread flour. Now on day nine, I see no measurable difference, though that wasn't the case up to this point.
If you're interested in following the process (with detailed photos), you can do so on my blog: www.theluckyfox.blogspot.com. Just click on the category "Starter Trials" to the right.
Debra Wink's starter writings are impressive, and I highly recommend them. They can be found on TFL here: www.thefreshloaf.com/node/10856/
Debra clearly understands this process.