One of the cool things about keeping killifishes is that most people know nothing about them. These creatures are quite a bit tougher to keep than the mass-bred fishes you can get at the big box stores. Many of them are annuals, meaning their lifespan is somewhere between 10 and 15 months. That means you must breed them if you want to keep them for any length of time.
Killis spawn in a couple of different ways. Some spawn in plants, where aquarists can substitute a mop made from certain kinds of yarn. The fish will lay eggs on that yarn, which can be removed for easy harvesting of the eggs. (Harvesting ensures a better survival rate as parents often eat their newborns.) Others spawn in substrate, which aquarists have found peat to be a good substitute for natural mud. Again, this facilitates harvesting for improved survival.
Many of the substrate spawners produce eggs that go through a diapause phase. That is to say, a length of time where nature hits the pause button on development. These fishes are adapted to live in temporary bodies of water, which explains much. No point in having the ability to live several years if your water dries up annually. Similarly, when the water is gone, eggs in diapause can be protected by the mud they had been buried in. The eggs remain in diapause until the wet season comes along and refills the body of water.
Diapause also comes in handy for distributing fishes. While live fishes can be shipped, it is bulky and can get expensive quickly. The recipient must be available to acclimate the fishes into their new homes immediately on arrival. Eggs in diapause, on the other hand, can be mailed in a padded envelope provided the temperatures aren’t too extreme on either end. (In my case, I have to receive eggs in the fall and spring because summer in this desert gets way too hot for the eggs to survive that time of year.
Not long ago, I received two clutches of eggs. One of them is the species Hypsolebia fulminantes, which I am scheduled to wet tomorrow. If you wet the eggs too early, it generally spoils the eggs. You can see a picture of an adult specimen on this guy’s flickr account.
Once we have fry swimming about, the peat and unhatched eggs are removed, water squeezed out, and we try again in a month. Nature provides multiple diapause durations to account for variability in rainfall. It would suck to hatch all the eggs the first go, then have the lake dry up again before the fish were old enough to spawn.
Wetting day is exciting for a fishkeeper, because hopefully a new colony of fish will be produced, and that’s always cool to observe and maintain.
Tomorrow, I will dump the bag of peat into a bowl and add water. If all goes well, in a few hours, I’ll have hungry little fry swimming about.
