Although keeping other G gymnogenys, I'd do the following:
1 keep them cool in winter - around 10 C, and than, when in summer they get warm, they will breed. Females do the caring for the fry, and as soon as the eggs hatch, and the fry (larvae) are developed - that is in 1 sometimes 2 days - I net them into a tank of 50 * 50 cm footprint - same temp, same water
Afer a while the female will release the fry, but I leave them alone, I only feed them. Approx 1 month after the fry are first seen, the female will relax her breeding behaviour, and netting her out is easy.
The fry are kept in this tank untill at least 2 cm and may be combined than, 1 species in a tank, obviously
The males of these species will not tolerate each other, and the females do look quite similar - therefore, NEVER combine them, or risk combining them (be certain a tank i free of fry, before using it for any other purpose, for instance)
the fry does grow slowly, very slowly indeed - My G gymnogenys of 5 cm were born in 2008