Many species of killifish are not substrate spawners and do not require their eggs to go through a dry "hibernation" phase. These can be easily harvested from spawning mops made from yarn. For those plant spawners, this mop can be suspended near the top of the tank. For those who spawn near the bottom (Fp. Garderni and Aph. Australe) this spawning mop can rest on the bottom of the tank.
Plant spawning killifish such as those of genus of Aphyosemion, Applochelius, Epiplatys and generally Fundulopanchax (notably Gardneri) lay their adhesive eggs singly among the fine leaves and roots of plants. Thus in a well planted aquarium, emphasis with a bed of Java Moss, you can let natural selection choose how many vigorous and viable fry you wish to raise. But if you wish to save eggs, raise fry until they are large enough to "make it" in the aquarium, and to increase the number of your species' population, you may wish to consider collecting eggs in spawning mops.
Since killifish eggs are readily seen and durable (with gentle handling) because of the cell membrane thickness of the eggs, they can be easily collected by hand and hatched in another small container, permitting removal of eggs that have fungus, the fry to hatch, get enough food (microworms, vinegar eels, newly hatched brine shrimp nauplii) and a chance to reach a size where they can survive.
Making a Spawning Mop
To make the eggs easy to find, you simply need to provide the yarn spawning mop as a substitute for natural plants. It's easy to make a spawning mop. Although some say color doesn't matter, I suggest using a dark green for floating mops and a dark green or brown mop if you drop it in the tank to sink to the bottom, or plant the bulb-head of the mop in the gravel to simulate plants and grasses.
First, wind a length of colorfast yarn around a book or another object about 8-10 inches long. Make about two dozen loops. Leave about 4-6 inches in your final loop. Snip the yarn and gently slide your loop off your object. With the extra 8-10 inches you left, wrap this around one end of your loop, leave about 4-6 inches and tie a granny knot, securing this end. Snip the other end of the loop. You can tie the knotted end of the mop around a cork (or to something at the top of the tank) if you wish the mop to float, or leave it as it is and let it sink. Boil the mop to sterilize it and then after it cools, place it in your aquarium.
Harvesting the Eggs
After the killies have spawned (2-3 days), remove the mop, let it drain for a moment and place it on a towel or newspaper to continue to dry until moist. Then, gently inspect the spawning mops for fish eggs. Good fertilized eggs look like tiny drops of water which transparent and shiny. Eggs that have begun to fungus will be milky and cloudy.
Removing the eggs is easy. Gently use your finger nail to loosen the egg from the mop. Once you see the egg on your finger, simply dip your finger into the water in your small collecting container. A used margarine tub or tupperware is excellent for this, but should not be washed with soap, rather very warm salt water, as is true for your hands. Rinse this and your hands thoroughly.
Incubating the Eggs
With these plant spawners, it usually takes about 21 days (range is 10-28 days depending upon species and water temperature) before the fry begin hatching. You can incubate the plant spawner eggs in several different ways.
The first method is known as water incubation. You simply keep the eggs stored in a small container of water. As the eggs develop, some die, are infertile and fungus. These turn a cloudy milky white and eventually get covered with hairy fungus. The eggs that have fungus should be removed lest they infect the remain good eggs. You should change about half of the water in your hatching container about every other day. It is also helpful if you can leave an airstone in there with a low output to gently keep plenty of oxygen and to slowly circulate the water.
Fertilized and viable eggs gradually start showing little black specks (malanifores) and within a few days you can see the developing embryo. A viable embryo will be "eyes up" and at the top of the egg, as you look down upon it. As the eyes and the entire embryo develop, you'll see when they are ready to hatch.
Hatching the Eggs
When the fry are ready to hatch, slowly add some seasoned water and a little food in the form of a few microworms, vinegar eels, or newly hatched brine shrimp nauplii. Do note that all killies generally can be incubated using the peat method (certainly very moist peat) and the peat method does give you some control of hatching dates of both annuals and non-annual killifish.
Killifish occasionally have difficulties in hatching. They go into a hibernation known as "diapause" and these fry are likely to die in their shells unless you do a few things to try to help them hatch. There are several things you can do.
One is to remove the airstone and let them stand for a few hours. If you don't begin seeing fry hatch, you can blow CO2 into the water with a straw. I've also seen a lot of killifish begin to hatch, simply by putting in a little food (microworms, vinegar eels and newly hatched brine shrimp nauplii), which seems to encourage them that it is time to hatch as there is a food supply to sustain and grow the fry. If none of these forced-hatching methods work, you can put the eggs into a small container and walk around with them in your pocket.
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