As usual, OFL gives the best advice.
Is there any way for you to return the cories, or upgrade to a larger tank? If you bought one 20 gallon tank you could divide it and have a betta and 4-6 cories in each section.
Is there any way for you to return the cories, or upgrade to a larger tank? If you bought one 20 gallon tank you could divide it and have a betta and 4-6 cories in each section.