I have a 30L that houses my spawning pair or super red BN and a 40 breeder that holds 5-6 adult brown BN, only 2 are males. Plenty of fry growing out in both tanks. The 30 also holds my endler's livebearers, many dozens of those, most are small/fry though. I feed them NLS Grow pellets, spirulina flake, and canned green beans once weekly.
All my breeding/growout tanks have large amounts of Najas or hornwort as well as duckweed to help maintain water quality.