it depends on the betta...i have one betta that is fine with them(even leaves the minute babies alone)...the other betta immediately tried to attack and kill them so i had to rescue them... both are in 10 gallons so space is not an issue....in fact during the summer before the ac was turned on the tank got up to about 82 and the shrimp became agressive and ripped my bettas fins in a couple places which they have been known to do in higher temps