If you want that many you will need more like a 125 or a proper pond setup imo.
Keeping turtles together can be tricky. You sometimes will get lucky and they get along, and sometimes you won't. But providing them with enough space is essential if you want any shot of keeping them long-term.
Males tend to be aggressive to other males. Females less so usually but they can still be aggressive, and they grow larger in many species.
Here's a setup I built for two red eared sliders years ago. They were male and female and got along well for years in this 72 gallon.
Keeping turtles together can be tricky. You sometimes will get lucky and they get along, and sometimes you won't. But providing them with enough space is essential if you want any shot of keeping them long-term.
Males tend to be aggressive to other males. Females less so usually but they can still be aggressive, and they grow larger in many species.
Here's a setup I built for two red eared sliders years ago. They were male and female and got along well for years in this 72 gallon.