Hello, i have a male common bn and once i get a female i would like to breed them. I want to put the fry after they are born in a 40 litre tank but it is already inhabited by 2 black skirt tetras, 2 guppies (male and female), and a ghost catfish. will any of these fish eat the fry? i could keep the male bn with the fry if that would help.

the tetra might be an issue. tetra are very nasty little fish.

once they are a bit bigger they should be ok

basically any fish with a big enough mouth to fit the fry in will eat them. i keep small fish like guppies in my bn breeding tank. as doug has stated your black skirt tetras (aka black widow tetras) would be the bigger problem as large tetras have a tendency to be nippy