Would it be possible to have a betta sorority with 5 female bettas and 6 Pygmy/dwarf cories in a 20g long? The tank will be heavily planted and at the place where I get the bettas, they will already be living in the same tank prior to me buying them. I will also have another divided 20g tank to divide into 4 just in case anything happens. Will the tank be overstocked like this? Should I get a 30g for this to work? Thanks in advance!