would 4 sterbai cories be able to go in a 15g tank along with 5 female bettas?
I go by the old rule of one adult corydoras per 5 gallons which is probably conservative; for a 20 gallon four should not be a problem. Last winter I raised ten (10) C. sterbai juvies in a 6 gallon. Currently I am raising about 18-20 C. sterbai (6 albinos and the rest regular) in a 10 gallon and I have about 7 adult C. sterbai in my 30 gallon.
Juvie C. sterbai in 6 gallon