Tips for colony breeding? Ricefish, livebearers, etc...

[Mahi27]

Hi all. I originally wanted to make a post just to ask for help with my Japanese ricefish tank, but I'd like to make the discussion open to colony breeding more broadly.

In theory, I really like the idea of colony breeding -- which, as I understand it, is the practice of setting up a tank in which you keep a species. That species spawns, and instead of removing the eggs/spawning mop/adult fish, you aim to have a tank with enough cover, natural food sources (biofilm and microfauna), and generally "well-seasoned" conditions such that baby fish can reach adulthood.

So, again, I really like this idea because it feels natural and lower-effort than actively breeding. I'm also limited on space so not having to maintain separate grow-out tanks is appealing.

The problem is that I haven't had any fry survive in my tank, which has been set up since mid-June and stocked since July. Why could this be? I'm attaching pictures so people get a sense of what condition the tank is in. It's densely vegetated and stocked only with ricefish, cherry shrimp, and snails. Moss everywhere. I feed 2x daily Xtreme Nano. I've seen day-old fry here and there, tiny little things just barely hatched out. But eventually they disappear. On the other hand, I've taken egg-covered moss out a couple times and moved it to a shrimp-only tank; I've grown out baby ricefish this way, but not in their original tank.

Any ideas on what I can try doing differently? Do I need to give up on my ideal of colony breeding if I want ricefish babies?

[Levi_Aquatics]

I would feed more food more frequently because if the adults are hungry they are more likely to prey on the fry. 

[PedroPete]

I know what you mean - I have had the same experience @Mahi27. My colonies of Medaka don’t produce fry hardly ever, but if I remove the Java moss with eggs to another tank, I get boatloads of babies. My Medaka are in 20 gallon indoor ponds (IKEA storage bins) as well as in 6 gallon trays/tubs that are kept outdoors for three seasons. 

[Mahi27]

Interesting! I'm going to maybe do a bit of what's in both replies -- feed heavier on the main tank, but continue to harvest eggs whenever I feel like raising up a batch of babies. I guess in a way this is good, in that I'll never be overrun with too many babies. 

[gardenman]

Small fry need small food and lots of it. They're competing with the shrimp and other life in your tank for that food while other fish are looking at them as food. Larger livebearers are easier to raise as they can eat bigger food early on and don't need the smaller stuff. Odds are your HOB is filtering out much of the free floating/suspended food that the fry could eat. I might try removing the HOB and see if that improves your success rate.

[SFF.Aquatics]

Make sure the HOB has a prefilter too. Otherwise, the fry could be sucked up. I also agree to feed more and more often. you might need to increase water changes but be careful not to suck up fry. Maybe add a snail or two to eat up any uneaten food.