(Source: M. Westerfield from Zebrafish Book 5th Edition)
Collect embryos by siphoning them up from among the marbles at the bottom of the tank. Make the siphon from a plastic or glass tube (1 cm i.d. and 30-50 cm long) covered at one end with a piece of Tygon tubing to protect it from breaking. To catch the embryos, direct the stream of water, started by mouth suction, through a medium-mesh nylon net. After sweeping the bottom of the tank from side-to-side with the siphon, invert the net over a Petri dish or finger bowl filled with 10% Hank's saline (see RECIPES). The embryos will fall off the net when they come into contact with the saline. To help prevent mold, clean the embryos right away by rinsing them several times with fresh 10% Hank's. Remove feces and other residue with forceps. If problems with mold are still encountered, the embryos can be washed at this point for 2 minutes with a 0.5% solution of bleach.
Figure 1. Embryo siphon.