The betta already semi full grown? Really comes down to the temperament (trial and error) if he is.
If you wish to improve the odds in a community get yourself a juvenile baby, the ones they sell at Petco that look like tiny guppies. My present Veil Tail was raised in a 15 this way alongside ghost shrimp, cherry shrimp, neons and white clouds. He was the runt of the litter as even a small ghost shrimp used to scare him off. These days he's full grown and can easily fit 1 or 2 shrimp in his mouth but to my delight he completely ignores em, probably cause he was raised alongside as a pup.
On the other hand, there is zero chance my shrimp would survive with my Crowntail sitting alone in his 5 gallon, he'd probably devour them up quickly