That certainly is a beautiful Betta, my first betta looked very similar, that was my first ever tank and fish! I used to feed my beetas with daphnia and mosquito larvae, before I moved, I don't have a pond here. so unfortunately my new betta only gets 'bug bites' now, though he may be eating baby red cherry shrimp from his tank when I'm not looking - the numbers of shrimp have decreased but the tank os very densely planted (translation to reality - overgrown)? I see some mosquito larvae in your photo and remember watching my betta chasing them around, great to watch and means less mosquitoes around, so a double win?
Those shrimp do look black, but blue velvet can be virtually black so maybe that is what they are. I especially like the ones with the brown stripe along their back!
I also used to collect dry leaves from outside for the shrimps, mainly oak but I thiink there were some mulberry occasionally? I used to have that floating plant you have as well but the roots grew so fast it was a weekly job trimming them so stopped using those when I moved. Is that in one of your outside tubs as I see some duckweed in there also? What is kept in there, I see a red cherry shrimp or two I think?