Huppert et al. analyzed a simple model describing bottom-up control of phytoplankton blooms. While we appreciate the mathematical aspects of this article, we feel that the fit of their model to data of Lake Kinneret is overly optimistic because the time axis was rescaled in an arbitrary way. Furthermore, one of the main conclusions of the article (bottom-up control is more likely to occur than top-down control) cannot, in our opinion, be drawn from a minimal model because such a model focuses on one explanation. It cannot be used to reveal the relative importance of alternative explanations.