Patterning of zebrafish and other vertebrate embryos proceeds according to consistent, predictable developmental time courses. Because zebrafish spawn primarily during the first few hours after dawn, many important developmental stages typically occur during the middle of the night. As an automatic, accurate way to fix embryos at these inconvenient times, we have developed the Time Reaper 5-Channel Automatic Liquid Dispenser (TimeR). The TimeR delivers up to 50 mL of liquid to embryos in a Petri dish at preset times. We have used the TimeR to deliver paraformaldehyde and fix zebrafish embryos at different stages of development. We find that the pattern of expression for a number of genes is indistinguishable between embryos fixed manually and with the TimeR. The TimeR is also suitable for fixing embryos for whole-mount immunostaining, but care needs to be taken to find conditions that preserve the antibody's epitope. The TimeR is inexpensive to make, and can be constructed using tools present in most machine shops. In addition to fixing embryos, the TimeR will be useful for any experiment that requires automatic delivery of milliliter amounts of liquid.