Who Gives A Fish Forums

Twice a week sounds good if the tank's small. Just monitor your betta's behavior—if they're hiding more or flaring at the vacuum, slow down. Also, check your filter media; sometimes it needs a rinse in tank water to keep flow steady.

I'd start with a partial water change, maybe 25-30%. Use a gravel vacuum to clean the substrate without disturbing your betta too much. For the algae, a soft sponge or algae scraper works, just avoid chemicals. How often are you doing water changes now?