The article is an autophenomenographic-poetic, eco-critical meditation on diatoms. It combines a reflection on the role of this algae species in the author’s posthuman modes of mourning her passed away lesbian life partner, with a discussion of philosopher Isabelle Stengers’s notion of wonder in materialist science, defined as open-ended approaches to unexpected diversity. Diatoms are single-celled aquatic algae, a kind of phytoplankton, which, due to their ability to photosynthesize, have been categorized as plantlike. However, in 2011, it was discovered that diatoms have an animal-like urea cycle, assumed to provide robustness in times of nutrient scarcity, but also making diatoms resist categorizations as either plant- or animal-like. Taking the author’s entangled commitments to human–diatom relations and this unexpected discovery as entrance point to reflect on wonder in technoscience, the article discusses ways of shifting from instrumentalizing to wonder-based algae research, asking if speculative art and poetry can open new horizons, interpellating pathways to ethically care for diatoms. The article introduces two poems, articulating the author’s relations to the diatoms of Limfjorden, the Danish fjord, where her partner’s ashes are spread. The author’s autophenomenographic-poetic work is also brought in conversation with feminist technoscience scholar Astrid Schrader’s critical research on utilitarian instrumentalism in current harmful algal blooms (HABs) research.