Wanted to share my recent experiences breeding as a sort of journal.
For background, we purchased 7 CPDs several months ago. They were in a 10g tank on their own except snails. The tank was heavily planted with a big moss "tree." Water was just dechlorinated tap. Injected CO2 for the plants, 9 hour photoperiod. Non-heated with temperatures in the low 70s. We found fry in the moss regularly. The way the moss was shaped provided a sort of moss breeding box where the fry were undisturbed by the adults. At the time I was feeding just crushed flake and pellets.
Here is a video of them feeding on baby brine so that you can see the setup:
In only a few months, our 7 fish became 28. Luckily we were already in the process of setting up a 40g, because they were getting cramped in the 10g.
Now, in the 40g, we have CPDs and Clown Killies. Soon we will have shrimp and other fish as well. We moved the tree to the new scape since we liked the design:
I consistently see the fish breeding above the moss, but the few fry we saw free-swimming have been eaten by the other fish since the moss breeder box is no longer present. We wanted to still have some breeding, so we are trying removing the eggs and putting them in another tank until they are a safe size. Some might be killifish egs, but I think it is primarily CPD.
Here are two males sparring around the breeding site. Didn't want to get too close and spook them, sorry for quality: https://i.imgur.com/RxVAEhj.mp4
Here is a photo of an egg in the moss. I don't know which eggs are which. One has white spots in the egg, like this. The others are crystal clear with only minor black flecks throughout.
I extracted the eggs from the tank using a turkey baster. The white ones were more adhesive, but the clear ones fall right off. I managed to get maybe 10-12 of the clear eggs. We put the eggs in the quarantine tank in a breeder box (to keep the shrimp off of them). Excuse the quality. These eggs are super tiny and are clear, so it is difficult to focus on them.
Here is a video showing movement inside the egg:
Here are a couple videos showing non-free swimming fry. You can see the tail and the yolk sac. They look more like tadpoles than fish at this point.
Hope that they will be able to hatch out and survive in this tank. The tank has been set up for many months and has many plants. Hope there are enough microorganisms to feed on. We will use egg yolk and vinegar eels to help them out.
I will keep updating as time goes. Since these are a result of several females and males over several days, the timing will be staggered. Most sources report a couple of days to hatch and a couple more days to become free swimming. Since we already have at least two that have hatched, we should see some free-swimming soon.