(Source: R. BreMiller from Zebrafish Book 5th Edition)
1. Fix animals as desired.
2. Wash in fix buffer, 3 times for 5 minutes each wash.
3. Soak fixed fish in 30% sucrose until they sink.
4. Transfer fish to embedding chamber (plastic test tube stoppers or inverted Beem capsules whose tips have been cut off) filled with OCT cryostat embedding medium (Tissue Tek®).
5. Freeze chamber by dipping it slowly and gradually into liquid N2.
6. Frozen blocks can be stored at -70°C if they are wrapped well so that the tissue does not dehydrate.
7. Cut 10-20 μm sections on a cryostat at -20°C, transfer them to subbed slides and let them dry completely.
8. Sections can be stored at -20°C in a sealed slide box.