Do you feed your Heterandria formosa live food? Mine Neoheterandria elegans didn't really want to breed until I started hatching artemia for them. Recently I switched to Grindal worms and these seem to be even better. Also what's the tank temperature? Heterandria likes it on the cooler side from what I read about them.Formosa does not want to breed.
Therefore, I added rice fish.
I have no personal experience with them, but read a couple of articles/first hand experience reports and from what I recall, they do best at about 20-22C. 24C should be still fine.What you write is very interesting.
The temperature is room, I do not specifically heat and do not cool - now t+24C.
In summer, I feed live Daphnia, in winter - Drosophila.
I do not breed worms - it is very difficult.
This sounds like a wonderful and memorable tank. Nature at its best!I once did that using only garden soil..sifted so it was just the clay soils we have. No covering at all. By a window,with only one of the small bulb water lilies and a male Betta...So other plants that I can't recall.
What I remember most was that I would feed all my fish in multiple conventional tanks live worms and brine shrimp- cheap here by San Francisco bay. After he are all he could...I would put more in. A few hours later,the worms were half in the soil and half out..wiggling their red bodys. Sun by the window caused pearling.
That must have been the early 80's.
btw,The water with no filter at all..was semi clear. When it had no fish..rotifers showed up,daphnia.