HfACR1 corresponds to a red-shifted light-gated anion channel protein from Hondaea fermentalgiana strain FCC1311. It can be used as an optogenetic tool to inhibit neuron activity; the peak activation wavelength of the native HfACR1 protein is 595nm, but the peak can be shifted a further 15nm to red (to 610nm) if HfACR1 is fused to EYFP (PMID:32873643).