This is what is saw on aqadvisor for a betta in a 2.5 g with a mini bow filter. Is this accurate?
Note: Betta [Male] may jump - lids are recommended. They can become stressful under presence of too many shoaling species. Try to keep under 1 shoal if the tank is small. Individual bettas may exhibit varying degrees of aggression and care should be taken that exceptionally aggressive/territorial fish be separated from a community before any damage may occur.
Recommended temperature range: 75.2 - 86 F. [Display in Celsius]
Recommended pH range: 6 - 8.
Recommended hardness range: 5 - 15 dH.
You have plenty of aquarium filtration capacity.
Your aquarium filtration capacity for above selected species is 136%.
Recommended water change schedule: 17% per week.
Your aquarium stocking level is 100%