Am I taking good care of my betta fish?

I love my betta fish! He is a male and is beatiful and cheers me up all the time! Everytime I come to see him he will swim around like craz and flap his gills and try and talk to my by opening his mouth i giggle my nose on his tank and he does the same thing! Today i was watching some videos about how Walmart is so cruel to the bettas and that made me question whther im taking good care of my fish or not. First of all he is always down or up in kis aquarium and doesnt move alot but if i come closer or if he seems me coming then he gets crazy and happy!! Second i put some seashells on his tank and usually it gets moldy and green but 2 days after i clean it and he is fine! And im worried his space is too small he has room to swim lots of it! But its not like a huge tank and the lady at the petstore told me not to get a huge tank because bettas dont like it so he has alot of green and colourfull decorations just not a huge tank! Oh and i dont want him to starve to everyday i feed him either 3 or 2 bettabites am i taking good care of him? If not tell me how I can because i love him soo much!<3