1. Fertilized eggs darken gradually
- In less than 24 hours, fertilized fish eggs will slightly change in color. You will notice that the translucent spheres are now faintly orange or beige in color.
If you find any white eggs the following morning, they are most likely unfertilized, and unfortunately non-viable. They must be removed promptly.
2. Developing embryo visible in the egg:
- If you examine the fertilized fish eggs closely around 24-48 hours, you will see tiny little dark dots forming in the center of the eggs. These are the fish embryo's eyes developing! Other parts of the embryo will start to form as well.
3. Tail begins to form:
- Several more hours later, a tiny elongated shadow resembling a tail-bud can be observed. This is an indication of healthy development.
4. Blood vessels and heartbeat are now prominent:
- Now, you may be able to detect blood vessels forming throughout the exterior of the growing fish embryo. They are visible thanks to the transparent membrane, and you may even be able to witness these tiny little vessels pulsate. It’s a little heart beating! As long as you find these in over half of the eggs, you can expect those fish eggs to hatch happily.
5. Eyes fully formed:
- The eyes of the fish embryo continue to develop and within a few days become almost black in color.
6. Free swimming fry hatch:
- Usually, most eggs hatch between 2 to 5 days depending on the species. Upon hatching, the tiny fry will be almost perfectly round with a long dangling yolk sac.