I think that RO or soft water is a trigger. Both times that I kept them, they lived for a long time, grew big (like 6-7"!) and did lots of spawning activities including cleaning rocks and pots... just never spawned. I didn't have or use RO water, which is probably what they needed.
Also, as you can tell, they're really shy fish. They'll also beat the crap out of each other...and eat other smaller fish.
Here's what I'd do if I had to try them again:
- Set the group up in a 4' tank (75g if you can spare it) with subdued lighting, calm-ish water movement and lots of hiding spots (driftwood, some pots and some leafy plants)
- Let the water get full of tannin and do regular say 30% water changes weekly with attention to cleaning the substrate. A big water change before a storm is when mine would go through the motions.
- Watch overfeeding them. They're really messy and picky eaters (they dart out and grab food and leave pieces everywhere). Maybe get some giant danios or decent-sized barbs to eat excess / missed food. Mine killed rainbowfish, small danios and livebearers (goodied and mollies), so they need something tough and fast.
I kept them in a species tank and also in a 6' 150g with medium new worlds. The 150g was too active for them. They came closest to spawning in the species tank.
They seem to establish pretty strong pair bonds and are supposed to spawn on plant leaves. Mine hung out in an overturned flower pot (with a crack for a door).
Really look forward to seeing yours progress as they grow!
Matt