I just lost a female betta in my sorority to old age (curse of buying petstore fish, often they aren't exactly young) and was thinking of replacing her with a baby betta from petco (all of my female bettas are from my local petco, I know the guy who works there (he's also the manager) and he is an aquarium enthusiast. He actually takes time and effort to care for them and refuses to allow bettas to be sold to people who are going to put them into a tank smaller than 2 gallons, they've gone from 20 dead fish a day to 1 or 2 a week on average since he took over.)

anyways... I want to know if this would be a very BAD idea. The other females have shown very little aggression towards one another and are not at all aggressive to their tank mates (nor vice-versa) and my tank is very well planted with plenty of decoration besides the live plants and driftwood (for my plecos) to ensure that everyone has places to hide and destress. I was thinking it would be nice to get a "surprise" as the baby bettas are generally a muddy brown colour (though some of the older ones have started to show their adult colours in the cups) but if there's a big chance that my other girls would tear into the baby/babies (I may get more than one just to cover other future deaths as I don't want my numbers going below 5 to prevent fights and stress, I do try to keep them odd but I had even numbers for a long time due to a previous death and still had no fighting) then I'll just get adult females instead.