Nothobranchius killifish breeds easily. The females are prolific egg-laying machines. A fish with such a short life span will, by nature, not be fussy about sexual partners or water conditions during spawning. There are many different types of breeding bowls you can use. A simple plastic bowl (ice cream tub) that comes with a lid is the most suitable. The lid helps prevent the peat moss from being scattered all over the tank when the killifish are spawning. Cut a round hole in the lid to a diameter of about 5 cm. Do not cut too small a hole as the killifish can injure themselves scrapping along the edges when they enter and leave the bowl. When conditioned well on live food, Nothos become sexually matured in about 2 months. Separate the males from the females if you are not ready to collect their eggs because in the absence of a breeding bowl, Nothos killifish will lay their eggs in the gravel or on the bottom of bare tanks.I will usually put one male with several females into a bare tank of about 20 litres when I want to breed the killifish. (That’s the way how it should be for us humans too, don’t you think? I wish.) To prevent velvet, I add 2 tablespoons of salt to the water. I find that velvet always strikes when the fish are in a breeding tank. I’m not sure but I think the peat moss softens and acidifies the water, thereby creating the conditions in which velvet thrives. Peat moss is available in most nurseries and some supermarkets. Do not confuse peat moss with peat.The former is fluffier. You can also use peat but it won’t be suitable for killifish that are “peat divers”. Before putting the peat moss into the breeding bowl, boil it first. This sterilises the peat and removes the oil. Cool the peat moss with running water before putting it into the breeding bowl.Nothos killifish are “peat spawners”. They lay their eggs just slightly below the surface of the peat unlike
“peat divers” which actually dives head first deep into the peat to lay their eggs. If you are using a plastic container as a breeding bowl, put in a small rock to weigh it down. Rocks are useful as Nothos killifish like to press against something hard when they are spawning. Fill the bowl halfway with peat moss and top it up with water. Allow some time for the peat to sink and scoop away the floating debris. Gently put the bowl into the breeding tank. Some peat moss will usually float out from the bowl. Do not bother about siphoning away the loose peat as it’s going to be messy anyway when the fish starts spawning.If the fish are sexually matured and if they were not too stressed when transferred into the breeding tank, spawning takes place almost immediately.The male will cajole the females to go into the breeding bowl with him by flaring and showing off his colours. If the female is willing, she will swim into the bowl and the male will press her down until the lower halves of their bodies are buried underneath the peat moss. They will remain motionless for a while before making a jerking movement and separating. That would be the signal that an egg has been laid. A female will usually lay several eggs before leaving the bowl. One female can lay up to 30 eggs in a day. If you are using many females, there will be many eggs in the breeding bowl after a few days. But if you have only a pair, it would be better to leave the bowl in the tank for a week at least. I feed the killifish with live tubifex and baby brine shrimp when they are in the breeding tanks. Occasionally, I give them live bloodworms as a special treat. If you want to collect many eggs, feed only live food. Frozen food is not live food. Frozen food to a killifish would be like canned food to a human. It does nothing for the libido. If you don’t believe me, ask the killifish.I change the water frequently, about half the volume of water every 2 days. Killifish will lay many eggs if they are healthy and happy so keep the water in the breeding tanks clean and give them as varied a diet as possible.To keep the water in the breeding tank clear, I use a simple sponge filter. Sponge filter that is L shaped. It’s a good filter to use in a breeding tank as it can be attached to the sides of the tank, thereby saving space. When there’s peat moss in the tank, it’s advisable to wash the sponge filter frequently because it will choke in no time. But always use the tank water to do this as you don’t want to kill off the *good* bacteria living in the filter.