improving feeding variety will be good of course, but i think the reason for not getting any fry for so long is not about feeding.
maybe you should check the water parameters and the fact that you have lots of fish in there and probably couples do not get the time and space they need to spawn successfully. overpopulation of adults could also lead to eggs being eaten as soon as they are laid.
do you see fat females carrying eggs?
i will just state my setup and feeding in case it helps:
i have 10 adults (6M, 4F) in a 180 liters heavily planted, single species tank (plants include lots of moss) and i get lots of fry, while i feed only crashed tetra pro veg flakes. – no live food at all and no special fry food.
every other day, i pre-wet the flakes in a very weak liquid vitamin concentration.
fry are fat and active and grow ok.
i have seen adults chasing fry, but never eating them when they get close.
filter intakes are covered with materials finer than air driven filter sponge.
Ph 7,2, GH 9, KH 6, TDS 160ppm, Temp 25C, (CO2 for the plants on a Ph controller)