I maintain three natural pre-ferments in my refrigerator, a Camaldoli, an Ischia and a former Carl, nowadays a mixture of the three.
I usually feed them every two or three weeks, just by adding wheat flour and water, repeating the feeding by three times and returning the ferments to the refrigerator, as normal.
The past month I decided to use rye flour to refresh them. Wow, it was an explosion!
The ferments developed a lot and grew as popcorns.
This last week I used them as part of Pannetone recipe, and this one grew so fast and big that surprises me. (Pannetone recipe, directions and pics following asap).
Just to check, I repeated the recipe a couple of days after and the results were consistent, even using wheat flour to the last refresh.
Just based in this experience, I strongly recommend to anyone using natural pre-ferments, give to rye flour a try. It could be a pleasant surprise.