Fish for breeding tank

My red-hump eartheaters, which are in a 120-gallon community tank, have
bred at least once, but the fry quickly were eaten by other fish. I am
now setting up a 20-gallon breeding tank into which I will transfer my
females next time they start brooding. This is a tank I'd like to keep
up and running with fish that won't eat the eartheater fry - if there is
such a thing. My LFS has suggested cory cats. I like the idea, but
would like others to consider. Do small tetras (neons, green fire, etc)
get big enough that they'd go after the fry?

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