Many Killifish species live in environments subjected to seasonal drought. During the arid season, their streams and puddles will dry out and all the adult fish will die. The species will however survive, because during the rainy season the adult fish mated and the fertilized eggs were buried deep down in the mud. As long as the eggs stay resting in the dirt, they will hardly need any moist at all and can therefore survive until a new rainy season commence.
The facts described above are of vital importance if you want to hatch Killifish eggs. Sometimes, adding some water to the eggs will be enough and you will have a huge batch of hungry Killifish fry in no time. In many instance, this simple method will however prove insufficient. Even though you pour water over the eggs, they stubbornly refuse to hatch. Why is that? In order to understand why fertilized Killifish eggs sometimes decline to hatch, we must take a closer look at the life of a Killifish.
In many parts of the world, the onset of the rainy season is preceded by one or several showers. These showers are not large enough to turn a dry savannah into a lush pool of water and Killifish eggs that are triggered to hatch by the slightest raindrop will therefore die before they have a chance to reproduce. Through the course of evolution, such eggs have therefore been removed. If you want your Killifish eggs to hatch, you must therefore convince them that the rainy season has really begun and that there will be no shortage of water if they decide to hatch.
- Do not try to hatch the eggs too soon. Take a look at the environments from which your particular species hail. How long is the dry season in that part of the world? Some Killifish eggs are satisfied with two months of dry season, while others are used to waiting at least ten months in the wild. Many Killifish eggs are actually capable of surviving up to 20 months if they have to, since they live in regions where the rainy season is unreliable and sometimes skips a year.
- Provide the eggs with plenty of water. Remember, you are supposed to turn a savannah into a lake.
- The water should be deep enough to cause a change in pressure on the egg shells. This means a water depth of approximately 2 inches. (More water is not recommended since it can make it hard for the fry to reach the surface.)
- Use water that is cooler than the surrounding “mud”. In the wild, a heavy rain will normally decrease the temperature of the hot and arid soil dramatically. If your eggs have been stored at room temperature, a water temperature of 55-60 degrees F is recommended.
Following these four steps will normally make at least a part of the batch hatch. In the wild, different eggs have different survival tactics. Some eggs want to wait as long as possible, to know for sure that the rainy season has really started. Other eggs are less hesitant, because the first ones to emerge can start claiming territory, they will have time to grow larger than the others etcetera. Waiting too long can also make it impossible to complete a full life cycle before the dry season commences. Another problem connected to waiting is that if the puddle has time to get really deep, the fry will not be strong enough to swim to the surface to fill its swim bladder. In order to get the more hesitant eggs to hatch, there are a few tricks used by Killifish breeders that you can try out. Different breeders have had different success with these and more experimenting is needed before anyone can no for sure which ones that work best.
- Add infusoria to the water. In the wild, Killifish do not want to hatch until there is plenty of food. They have no yolk sacs and must therefore emerge to a virtual smorgasbord if they want to survive. When you add infusoria to the water, the infusoria will consume a lot of oxygen. Some breeders suspect that Killifish eggs can sense this change in oxygen-levels and decide to hatch.
- Add microworms to the mud/peat moss. Killifish may be able to detect vibrations caused by microworms and interpret them as a reliable indication of a true rainy season.
- Wiggle the mud/peatmoss around and break it up into smaller parts. This is what happens to mud that is suddenly blasted by heavy rains and water flow.
- If nothing works, put the peat moss back in its container and let it rest. Perhaps the eggs will be more eager to emerge after a few more weeks of dry season.
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