I will be putting my 3 male bettas into my 16 gal tank when its cycled. I want to keep the 10 gal, so i was thinking about getting some female bettas. Is 5 or 6 ok

Go with 5, odd numbers are better than even, and make sure it's very densely planted with lots of hidey holes!

I would recommend getting all 5 at once (be careful with water chemistry in that newly cycled tank though, thankfully Bettas aren't huge waste producers) from the same tank at the store. That way you can be fairly sure they're spawn siblings and more likely to get along. And to be a real pain, make sure to examine them closely as there may be plakat boys mixed in with the girls. Try to make sure you get ones that don't look like they have completely been through the wars! I have seen some girl tanks that must have had a plakat male or two mixed in, nipped fins everywhere!

A 10 gallon is too small for a group of bettas to do any good, but 5 or 6 would be nice in a 20 gallon. Odd and even makes no difference - that's one of those internet facts that just appeared somewhere. Every group will end up with slightly different results regardless of numbers.

5 is about right. Enough to spread out the aggression, but not overcrowd the tank. pets question and answers,www.5d2d.com

Although when you think about it, 3 males in the ten gal, with dividers, and the 5 or more females in the 16gal is actually a better spread. That way they all get about 3 gal each.

Ian

The 16 gallon is divided right? I woulod not keep a group of female bettas in anything less than 20 gallons, it's just too risky. You could have a single betta (male or female) with a small school of ember tetras or corydoras.

5 or 6 females are fine to have in that size tank, but I don't recommend putting the 3 males in one tank they will fight and Betta males normally fight until the other one is dead ...

you can have how many you wold like about 9.