Hello again,
As an update to my beginner fish (Gardneri) they are happy, healthy, and breeding like rabbits.
Problem is that I haven't had good luck with raising fry, or getting decent hatch rates.
(The fry that hatched and died are my fault, as I kept them in a tank with rice fish of the same age--turns out rice fish have much larger mouths and grow much faster)
Methylene blue (all kinds of different strengths) has not treated me well with the Fp Gardneri, and neither has putting the eggs in an established planted tank(bare bottom, gravel bottom, or gravel topped peat/dirt) .

I tried incubating on moist peat, but the "pure, unfertilized peat" that I picked up from my local nursery ended up having small amounts of mulch and other misc in it. Im not sure if this could contribute to unsuccessful incubation, but I'm willing to give it another shot with a peat that is known to work.
Maybe I'm grasping at straws here, but can someone point me to the peat or other medium that they use to incubate? Links appreciated.

Also, is there a way to tell if an egg is fertilized or not? Or is it just a matter of incubating them and seeing if they develop?

I order Jiffy 703 from Grower's Solution (https://growerssolution.com/). It works very well.

I have little success incubating on peat. For GAR I pick eggs and incubate in aquarium water. I try incubate in the dark so no algae grows on the eggs. I expect the problem is a young male with poor fertility. Typically, GAR eggs are very tough.

If you want, spawn them in an established tank with gravel on the bottom for 2 weeks and then remove the adults. This normally produces lots of fry.

Good luck!