i'm going to go with cons just because they have larger spawns than livebearers, though i suppose with cover to protect fry you can have multiple spawning livebearers in a single tank.
Mollies will breed in either. I've got a breeding pair in a brackish tank now and they are doing fantastic. Another nice thing I've noticed about Mollies, they don't eat as many of their own young as guppies do. My food breeder tank is well established though, so they have lots of organic matter to eat instead.
i'm going to go with cons just because they have larger spawns than livebearers, though i suppose with cover to protect fry you can have multiple spawning livebearers in a single tank.
That is what I am doing. Multiple livebreeders in a tank so as to greatly increase output. Sure some fry will get eaten and whatnot but the numbers game works out for me in the end.
I'm breeding cons right now and its incredibly easy in my 20g for the single pair. Only problems I've had so far is the female getting aggressive towards the male now that fry are in the tank & that I haven't seen either male or female eat much at all since the fry came.
She doesn't let him out of hiding much at all and he's taken to jumping a LOT over the past 2 days or so...
I think it all depends on the space and such you are willing to devote to breeding for feeders. I will have 2 20 gals going and the amount of breeding mollies in there will greatly outpace that of 2 pairs of convicts even with the number of fry eaten...
Though in terms of enjoyment to watch I think Cons take the bill. Get to see some interesting parenting and such as well as get feeders. I just dont want my wife to get attached to the cons and their babies. HA HA